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PERLAPI(1pm)           Perl Programmers Reference Guide           PERLAPI(1pm)




NAME

       perlapi - autogenerated documentation for the perl public API


DESCRIPTION

       This file contains most of the documentation of the perl public API, as
       generated by embed.pl.  Specifically, it is a listing of functions,
       macros, flags, and variables that may be used by extension writers.
       Besides perlintern and config.h, some items are listed here as being
       actually documented in another pod.

       At the end is a list of functions which have yet to be documented.
       Patches welcome!  The interfaces of these are subject to change without
       notice.

       Some of the functions documented here are consolidated so that a single
       entry serves for multiple functions which all do basically the same
       thing, but have some slight differences.  For example, one form might
       process magic, while another doesn't.  The name of each variation is
       listed at the top of the single entry.  But if all have the same
       signature (arguments and return type) except for their names, only the
       usage for the base form is shown.  If any one of the forms has a
       different signature (such as returning "const" or not) every function's
       signature is explicitly displayed.

       Anything not listed here or in the other mentioned pods is not part of
       the public API, and should not be used by extension writers at all.
       For these reasons, blindly using functions listed in proto.h is to be
       avoided when writing extensions.

       In Perl, unlike C, a string of characters may generally contain
       embedded "NUL" characters.  Sometimes in the documentation a Perl
       string is referred to as a "buffer" to distinguish it from a C string,
       but sometimes they are both just referred to as strings.

       Note that all Perl API global variables must be referenced with the
       "PL_" prefix.  Again, those not listed here are not to be used by
       extension writers, and can be changed or removed without notice; same
       with macros.  Some macros are provided for compatibility with the
       older, unadorned names, but this support may be disabled in a future
       release.

       Perl was originally written to handle US-ASCII only (that is characters
       whose ordinal numbers are in the range 0 - 127).  And documentation and
       comments may still use the term ASCII, when sometimes in fact the
       entire range from 0 - 255 is meant.

       The non-ASCII characters below 256 can have various meanings, depending
       on various things.  (See, most notably, perllocale.)  But usually the
       whole range can be referred to as ISO-8859-1.  Often, the term
       "Latin-1" (or "Latin1") is used as an equivalent for ISO-8859-1.  But
       some people treat "Latin1" as referring just to the characters in the
       range 128 through 255, or sometimes from 160 through 255.  This
       documentation uses "Latin1" and "Latin-1" to refer to all 256
       characters.

       Note that Perl can be compiled and run under either ASCII or EBCDIC
       (See perlebcdic).  Most of the documentation (and even comments in the
       code) ignore the EBCDIC possibility.  For almost all purposes the
       differences are transparent.  As an example, under EBCDIC, instead of
       UTF-8, UTF-EBCDIC is used to encode Unicode strings, and so whenever
       this documentation refers to "utf8" (and variants of that name,
       including in function names), it also (essentially transparently) means
       "UTF-EBCDIC".  But the ordinals of characters differ between ASCII,
       EBCDIC, and the UTF- encodings, and a string encoded in UTF-EBCDIC may
       occupy a different number of bytes than in UTF-8.

       The organization of this document is tentative and subject to change.
       Suggestions and patches welcome perl5-porters@perl.org
       <mailto:perl5-porters@perl.org>.

       The sections in this document currently are

       "AV Handling"
       "Callback Functions"
       "Casting"
       "Character case changing"
       "Character classification"
       "Compiler and Preprocessor information"
       "Compiler directives"
       "Compile-time scope hooks"
       "Concurrency"
       "COP Hint Hashes"
       "Custom Operators"
       "CV Handling"
       "Debugging"
       "Display functions"
       "Embedding and Interpreter Cloning"
       "Errno"
       "Exception Handling (simple) Macros"
       "Filesystem configuration values"
       "Floating point configuration values"
       "Formats"
       "General Configuration"
       "Global Variables"
       "GV Handling"
       "Hook manipulation"
       "HV Handling"
       "Input/Output"
       "Integer configuration values"
       "Lexer interface"
       "Locales"
       "Magic"
       "Memory Management"
       "MRO"
       "Multicall Functions"
       "Numeric Functions"
       "Optree construction"
       "Optree Manipulation Functions"
       "Pack and Unpack"
       "Pad Data Structures"
       "Password and Group access"
       "Paths to system commands"
       "Prototype information"
       "REGEXP Functions"
       "Signals"
       "Site configuration"
       "Sockets configuration values"
       "Source Filters"
       "Stack Manipulation Macros"
       "String Handling"
       "SV Flags"
       "SV Handling"
       "Time"
       "Typedef names"
       "Unicode Support"
       "Utility Functions"
       "Versioning"
       "Warning and Dieing"
       "XS"
       "Undocumented elements"

       The listing below is alphabetical, case insensitive.


AV Handling

       "AV"
           Described in perlguts.

       "AvARRAY"
           Returns a pointer to the AV's internal SV* array.

           This is useful for doing pointer arithmetic on the array.  If all
           you need is to look up an array element, then prefer "av_fetch".

            SV**  AvARRAY(AV* av)

       "av_clear"
           Frees all the elements of an array, leaving it empty.  The XS
           equivalent of "@array = ()".  See also "av_undef".

           Note that it is possible that the actions of a destructor called
           directly or indirectly by freeing an element of the array could
           cause the reference count of the array itself to be reduced (e.g.
           by deleting an entry in the symbol table). So it is a possibility
           that the AV could have been freed (or even reallocated) on return
           from the call unless you hold a reference to it.

            void  av_clear(AV *av)

       "av_count"
           Returns the number of elements in the array "av".  This is the true
           length of the array, including any undefined elements.  It is
           always the same as "av_top_index(av) + 1".

            Size_t  av_count(AV *av)

       "av_create_and_push"
           NOTE: "av_create_and_push" is experimental and may change or be
           removed without notice.

           Push an SV onto the end of the array, creating the array if
           necessary.  A small internal helper function to remove a commonly
           duplicated idiom.

           NOTE: "av_create_and_push" must be explicitly called as
           "Perl_av_create_and_push" with an "aTHX_" parameter.

            void  Perl_av_create_and_push(pTHX_ AV **const avp,
                                          SV *const val)

       "av_create_and_unshift_one"
           NOTE: "av_create_and_unshift_one" is experimental and may change or
           be removed without notice.

           Unshifts an SV onto the beginning of the array, creating the array
           if necessary.  A small internal helper function to remove a
           commonly duplicated idiom.

           NOTE: "av_create_and_unshift_one" must be explicitly called as
           "Perl_av_create_and_unshift_one" with an "aTHX_" parameter.

            SV**  Perl_av_create_and_unshift_one(pTHX_ AV **const avp,
                                                 SV *const val)

       "av_delete"
           Deletes the element indexed by "key" from the array, makes the
           element mortal, and returns it.  If "flags" equals "G_DISCARD", the
           element is freed and NULL is returned. NULL is also returned if
           "key" is out of range.

           Perl equivalent: "splice(@myarray, $key, 1, undef)" (with the
           "splice" in void context if "G_DISCARD" is present).

            SV*  av_delete(AV *av, SSize_t key, I32 flags)

       "av_exists"
           Returns true if the element indexed by "key" has been initialized.

           This relies on the fact that uninitialized array elements are set
           to "NULL".

           Perl equivalent: "exists($myarray[$key])".

            bool  av_exists(AV *av, SSize_t key)

       "av_extend"
           Pre-extend an array so that it is capable of storing values at
           indexes "0..key". Thus "av_extend(av,99)" guarantees that the array
           can store 100 elements, i.e. that "av_store(av, 0, sv)" through
           "av_store(av, 99, sv)" on a plain array will work without any
           further memory allocation.

           If the av argument is a tied array then will call the "EXTEND" tied
           array method with an argument of "(key+1)".

            void  av_extend(AV *av, SSize_t key)

       "av_fetch"
           Returns the SV at the specified index in the array.  The "key" is
           the index.  If lval is true, you are guaranteed to get a real SV
           back (in case it wasn't real before), which you can then modify.
           Check that the return value is non-null before dereferencing it to
           a "SV*".

           See "Understanding the Magic of Tied Hashes and Arrays" in perlguts
           for more information on how to use this function on tied arrays.

           The rough perl equivalent is $myarray[$key].

            SV**  av_fetch(AV *av, SSize_t key, I32 lval)

       "AvFILL"
           Same as "av_top_index" or "av_tindex".

            SSize_t  AvFILL(AV* av)

       "av_fill"
           Set the highest index in the array to the given number, equivalent
           to Perl's "$#array = $fill;".

           The number of elements in the array will be "fill + 1" after
           "av_fill()" returns.  If the array was previously shorter, then the
           additional elements appended are set to NULL.  If the array was
           longer, then the excess elements are freed.  "av_fill(av, -1)" is
           the same as "av_clear(av)".

            void  av_fill(AV *av, SSize_t fill)

       "av_len"
           Same as "av_top_index".  Note that, unlike what the name implies,
           it returns the maximum index in the array.  This is unlike
           "sv_len", which returns what you would expect.

           To get the true number of elements in the array, instead use
           "av_count".

            SSize_t  av_len(AV *av)

       "av_make"
           Creates a new AV and populates it with a list of SVs.  The SVs are
           copied into the array, so they may be freed after the call to
           "av_make".  The new AV will have a reference count of 1.

           Perl equivalent: "my @new_array = ($scalar1, $scalar2,
           $scalar3...);"

            AV*  av_make(SSize_t size, SV **strp)

       "av_pop"
           Removes one SV from the end of the array, reducing its size by one
           and returning the SV (transferring control of one reference count)
           to the caller.  Returns &PL_sv_undef if the array is empty.

           Perl equivalent: "pop(@myarray);"

            SV*  av_pop(AV *av)

       "av_push"
           Pushes an SV (transferring control of one reference count) onto the
           end of the array.  The array will grow automatically to accommodate
           the addition.

           Perl equivalent: "push @myarray, $val;".

            void  av_push(AV *av, SV *val)

       "av_shift"
           Removes one SV from the start of the array, reducing its size by
           one and returning the SV (transferring control of one reference
           count) to the caller.  Returns &PL_sv_undef if the array is empty.

           Perl equivalent: "shift(@myarray);"

            SV*  av_shift(AV *av)

       "av_store"
           Stores an SV in an array.  The array index is specified as "key".
           The return value will be "NULL" if the operation failed or if the
           value did not need to be actually stored within the array (as in
           the case of tied arrays).  Otherwise, it can be dereferenced to get
           the "SV*" that was stored there (= "val")).

           Note that the caller is responsible for suitably incrementing the
           reference count of "val" before the call, and decrementing it if
           the function returned "NULL".

           Approximate Perl equivalent: "splice(@myarray, $key, 1, $val)".

           See "Understanding the Magic of Tied Hashes and Arrays" in perlguts
           for more information on how to use this function on tied arrays.

            SV**  av_store(AV *av, SSize_t key, SV *val)

       "av_tindex"
       "av_top_index"
           These behave identically.  If the array "av" is empty, these return
           -1; otherwise they return the maximum value of the indices of all
           the array elements which are currently defined in "av".

           They process 'get' magic.

           The Perl equivalent for these is $#av.

           Use "av_count" to get the number of elements in an array.

            SSize_t  av_tindex(AV *av)

       "av_undef"
           Undefines the array. The XS equivalent of "undef(@array)".

           As well as freeing all the elements of the array (like
           "av_clear()"), this also frees the memory used by the av to store
           its list of scalars.

           See "av_clear" for a note about the array possibly being invalid on
           return.

            void  av_undef(AV *av)

       "av_unshift"
           Unshift the given number of "undef" values onto the beginning of
           the array.  The array will grow automatically to accommodate the
           addition.

           Perl equivalent: "unshift @myarray, ((undef) x $num);"

            void  av_unshift(AV *av, SSize_t num)

       "get_av"
           Returns the AV of the specified Perl global or package array with
           the given name (so it won't work on lexical variables).  "flags"
           are passed to "gv_fetchpv".  If "GV_ADD" is set and the Perl
           variable does not exist then it will be created.  If "flags" is
           zero and the variable does not exist then NULL is returned.

           Perl equivalent: "@{"$name"}".

           NOTE: the "perl_get_av()" form is deprecated.

            AV*  get_av(const char *name, I32 flags)

       "newAV"
           Creates a new AV.  The reference count is set to 1.

           Perl equivalent: "my @array;".

            AV*  newAV()

       "Nullav"
           "DEPRECATED!"  It is planned to remove "Nullav" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Null AV pointer.

           (deprecated - use "(AV *)NULL" instead)


Callback Functions

       "call_argv"
           Performs a callback to the specified named and package-scoped Perl
           subroutine with "argv" (a "NULL"-terminated array of strings) as
           arguments.  See perlcall.

           Approximate Perl equivalent: "&{"$sub_name"}(@$argv)".

           NOTE: the "perl_call_argv()" form is deprecated.

            I32  call_argv(const char* sub_name, I32 flags, char** argv)

       "call_method"
           Performs a callback to the specified Perl method.  The blessed
           object must be on the stack.  See perlcall.

           NOTE: the "perl_call_method()" form is deprecated.

            I32  call_method(const char* methname, I32 flags)

       "call_pv"
           Performs a callback to the specified Perl sub.  See perlcall.

           NOTE: the "perl_call_pv()" form is deprecated.

            I32  call_pv(const char* sub_name, I32 flags)

       "call_sv"
           Performs a callback to the Perl sub specified by the SV.

           If neither the "G_METHOD" nor "G_METHOD_NAMED" flag is supplied,
           the SV may be any of a CV, a GV, a reference to a CV, a reference
           to a GV or "SvPV(sv)" will be used as the name of the sub to call.

           If the "G_METHOD" flag is supplied, the SV may be a reference to a
           CV or "SvPV(sv)" will be used as the name of the method to call.

           If the "G_METHOD_NAMED" flag is supplied, "SvPV(sv)" will be used
           as the name of the method to call.

           Some other values are treated specially for internal use and should
           not be depended on.

           See perlcall.

           NOTE: the "perl_call_sv()" form is deprecated.

            I32  call_sv(SV* sv, volatile I32 flags)

       "ENTER"
           Opening bracket on a callback.  See "LEAVE" and perlcall.

              ENTER;

       "ENTER_with_name"
           Same as "ENTER", but when debugging is enabled it also associates
           the given literal string with the new scope.

              ENTER_with_name("name");

       "eval_pv"
           Tells Perl to "eval" the given string in scalar context and return
           an SV* result.

           NOTE: the "perl_eval_pv()" form is deprecated.

            SV*  eval_pv(const char* p, I32 croak_on_error)

       "eval_sv"
           Tells Perl to "eval" the string in the SV.  It supports the same
           flags as "call_sv", with the obvious exception of "G_EVAL".  See
           perlcall.

           The "G_RETHROW" flag can be used if you only need eval_sv() to
           execute code specified by a string, but not catch any errors.

           NOTE: the "perl_eval_sv()" form is deprecated.

            I32  eval_sv(SV* sv, I32 flags)

       "FREETMPS"
           Closing bracket for temporaries on a callback.  See "SAVETMPS" and
           perlcall.

              FREETMPS;

       "G_ARRAY"
           Described in perlcall.

       "G_DISCARD"
           Described in perlcall.

       "G_EVAL"
           Described in perlcall.

       "GIMME"
           "DEPRECATED!"  It is planned to remove "GIMME" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           A backward-compatible version of "GIMME_V" which can only return
           "G_SCALAR" or "G_ARRAY"; in a void context, it returns "G_SCALAR".
           Deprecated.  Use "GIMME_V" instead.

            U32  GIMME

       "GIMME_V"
           The XSUB-writer's equivalent to Perl's "wantarray".  Returns
           "G_VOID", "G_SCALAR" or "G_ARRAY" for void, scalar or list context,
           respectively.  See perlcall for a usage example.

            U32  GIMME_V

       "G_KEEPERR"
           Described in perlcall.

       "G_NOARGS"
           Described in perlcall.

       "G_SCALAR"
           Described in perlcall.

       "G_VOID"
           Described in perlcall.

       "LEAVE"
           Closing bracket on a callback.  See "ENTER" and perlcall.

              LEAVE;

       "LEAVE_with_name"
           Same as "LEAVE", but when debugging is enabled it first checks that
           the scope has the given name. "name" must be a literal string.

              LEAVE_with_name("name");

       "PL_errgv"
           Described in perlcall.

       "SAVETMPS"
           Opening bracket for temporaries on a callback.  See "FREETMPS" and
           perlcall.

              SAVETMPS;


Casting

       "cBOOL"
           Cast-to-bool.  A simple "(bool) expr" cast may not do the right
           thing: if "bool" is defined as "char", for example, then the cast
           from "int" is implementation-defined.

           "(bool)!!(cbool)" in a ternary triggers a bug in xlc on AIX

            bool  cBOOL(bool expr)

       "I_32"
           Cast an NV to I32 while avoiding undefined C behavior

            I32  I_32(NV what)

       "INT2PTR"
           Described in perlguts.

            type  INT2PTR(type, int value)

       "I_V"
           Cast an NV to IV while avoiding undefined C behavior

            IV  I_V(NV what)

       "Perl_cpeep_t"
           Described in perlguts.

       "PTR2IV"
           Described in perlguts.

            IV  PTR2IV(void * ptr)

       "PTR2nat"
           Described in perlguts.

            IV  PTR2nat(void *)

       "PTR2NV"
           Described in perlguts.

            NV  PTR2NV(void * ptr)

       "PTR2ul"
           Described in perlguts.

            unsigned long  PTR2ul(void *)

       "PTR2UV"
           Described in perlguts.

            UV  PTR2UV(void * ptr)

       "PTRV"
           Described in perlguts.

       "U_32"
           Cast an NV to U32 while avoiding undefined C behavior

            U32  U_32(NV what)

       "U_V"
           Cast an NV to UV while avoiding undefined C behavior

            UV  U_V(NV what)

       "XOP"
           Described in perlguts.


Character case changing

       Perl uses "full" Unicode case mappings.  This means that converting a
       single character to another case may result in a sequence of more than
       one character.  For example, the uppercase of "ss" (LATIN SMALL LETTER
       SHARP S) is the two character sequence "SS".  This presents some
       complications   The lowercase of all characters in the range 0..255 is
       a single character, and thus "toLOWER_L1" is furnished.  But,
       "toUPPER_L1" can't exist, as it couldn't return a valid result for all
       legal inputs.  Instead "toUPPER_uvchr" has an API that does allow every
       possible legal result to be returned.)  Likewise no other function that
       is crippled by not being able to give the correct results for the full
       range of possible inputs has been implemented here.

       "toFOLD"
           Converts the specified character to foldcase.  If the input is
           anything but an ASCII uppercase character, that input character
           itself is returned.  Variant "toFOLD_A" is equivalent.  (There is
           no equivalent "to_FOLD_L1" for the full Latin1 range, as the full
           generality of "toFOLD_uvchr" is needed there.)

            U8  toFOLD(U8 ch)

       "toFOLD_utf8"
       "toFOLD_utf8_safe"
           Converts the first UTF-8 encoded character in the sequence starting
           at "p" and extending no further than "e - 1" to its foldcase
           version, and stores that in UTF-8 in "s", and its length in bytes
           in "lenp".  Note that the buffer pointed to by "s" needs to be at
           least "UTF8_MAXBYTES_CASE+1" bytes since the foldcase version may
           be longer than the original character.

           The first code point of the foldcased version is returned (but
           note, as explained at the top of this section, that there may be
           more).

           It will not attempt to read beyond "e - 1", provided that the
           constraint "s < e" is true (this is asserted for in "-DDEBUGGING"
           builds).  If the UTF-8 for the input character is malformed in some
           way, the program may croak, or the function may return the
           REPLACEMENT CHARACTER, at the discretion of the implementation, and
           subject to change in future releases.

           "toFOLD_utf8_safe" is now just a different spelling of plain
           "toFOLD_utf8"

            UV  toFOLD_utf8(U8* p, U8* e, U8* s, STRLEN* lenp)

       "toFOLD_uvchr"
           Converts the code point "cp" to its foldcase version, and stores
           that in UTF-8 in "s", and its length in bytes in "lenp".  The code
           point is interpreted as native if less than 256; otherwise as
           Unicode.  Note that the buffer pointed to by "s" needs to be at
           least "UTF8_MAXBYTES_CASE+1" bytes since the foldcase version may
           be longer than the original character.

           The first code point of the foldcased version is returned (but
           note, as explained at the top of this section, that there may be
           more).

            UV  toFOLD_uvchr(UV cp, U8* s, STRLEN* lenp)

       "toLOWER"
       "toLOWER_A"
       "toLOWER_L1"
       "toLOWER_LATIN1"
       "toLOWER_LC"
       "toLOWER_uvchr"
       "toLOWER_utf8"
       "toLOWER_utf8_safe"
           These all return the lowercase of a character.  The differences are
           what domain they operate on, and whether the input is specified as
           a code point (those forms with a "cp" parameter) or as a UTF-8
           string (the others).  In the latter case, the code point to use is
           the first one in the buffer of UTF-8 encoded code points,
           delineated by the arguments "p .. e - 1".

           "toLOWER" and "toLOWER_A" are synonyms of each other.  They return
           the lowercase of any uppercase ASCII-range code point.  All other
           inputs are returned unchanged.  Since these are macros, the input
           type may be any integral one, and the output will occupy the same
           number of bits as the input.

           "toLOWER_L1" and "toLOWER_LATIN1" are synonyms of each other.  They
           behave identically as "toLOWER" for ASCII-range input.  But
           additionally will return the lowercase of any uppercase code point
           in the entire 0..255 range, assuming a Latin-1 encoding (or the
           EBCDIC equivalent on such platforms).

           "toLOWER_LC" returns the lowercase of the input code point
           according to the rules of the current POSIX locale.  Input code
           points outside the range 0..255 are returned unchanged.

           "toLOWER_uvchr" returns the lowercase of any Unicode code point.
           The return value is identical to that of "toLOWER_L1" for input
           code points in the 0..255 range.  The lowercase of the vast
           majority of Unicode code points is the same as the code point
           itself.  For these, and for code points above the legal Unicode
           maximum, this returns the input code point unchanged.  It
           additionally stores the UTF-8 of the result into the buffer
           beginning at "s", and its length in bytes into *lenp.  The caller
           must have made "s" large enough to contain at least
           "UTF8_MAXBYTES_CASE+1" bytes to avoid possible overflow.

           NOTE: the lowercase of a code point may be more than one code
           point.  The return value of this function is only the first of
           these.  The entire lowercase is returned in "s".  To determine if
           the result is more than a single code point, you can do something
           like this:

            uc = toLOWER_uvchr(cp, s, &len);
            if (len > UTF8SKIP(s)) { is multiple code points }
            else { is a single code point }

           "toLOWER_utf8" and "toLOWER_utf8_safe" are synonyms of each other.
           The only difference between these and "toLOWER_uvchr" is that the
           source for these is encoded in UTF-8, instead of being a code
           point.  It is passed as a buffer starting at "p", with "e" pointing
           to one byte beyond its end.  The "p" buffer may certainly contain
           more than one code point; but only the first one (up through
           "e - 1") is examined.  If the UTF-8 for the input character is
           malformed in some way, the program may croak, or the function may
           return the REPLACEMENT CHARACTER, at the discretion of the
           implementation, and subject to change in future releases.

            UV  toLOWER          (UV cp)
            UV  toLOWER_A        (UV cp)
            UV  toLOWER_L1       (UV cp)
            UV  toLOWER_LATIN1   (UV cp)
            UV  toLOWER_LC       (UV cp)
            UV  toLOWER_uvchr    (UV cp, U8* s, STRLEN* lenp)
            UV  toLOWER_utf8     (U8* p, U8* e, U8* s, STRLEN* lenp)
            UV  toLOWER_utf8_safe(U8* p, U8* e, U8* s, STRLEN* lenp)

       "toTITLE"
           Converts the specified character to titlecase.  If the input is
           anything but an ASCII lowercase character, that input character
           itself is returned.  Variant "toTITLE_A" is equivalent.  (There is
           no "toTITLE_L1" for the full Latin1 range, as the full generality
           of "toTITLE_uvchr" is needed there.  Titlecase is not a concept
           used in locale handling, so there is no functionality for that.)

            U8  toTITLE(U8 ch)

       "toTITLE_utf8"
       "toTITLE_utf8_safe"
           Convert the first UTF-8 encoded character in the sequence starting
           at "p" and extending no further than "e - 1" to its titlecase
           version, and stores that in UTF-8 in "s", and its length in bytes
           in "lenp".  Note that the buffer pointed to by "s" needs to be at
           least "UTF8_MAXBYTES_CASE+1" bytes since the titlecase version may
           be longer than the original character.

           The first code point of the titlecased version is returned (but
           note, as explained at the top of this section, that there may be
           more).

           It will not attempt to read beyond "e - 1", provided that the
           constraint "s < e" is true (this is asserted for in "-DDEBUGGING"
           builds).  If the UTF-8 for the input character is malformed in some
           way, the program may croak, or the function may return the
           REPLACEMENT CHARACTER, at the discretion of the implementation, and
           subject to change in future releases.

           "toTITLE_utf8_safe" is now just a different spelling of plain
           "toTITLE_utf8"

            UV  toTITLE_utf8(U8* p, U8* e, U8* s, STRLEN* lenp)

       "toTITLE_uvchr"
           Converts the code point "cp" to its titlecase version, and stores
           that in UTF-8 in "s", and its length in bytes in "lenp".  The code
           point is interpreted as native if less than 256; otherwise as
           Unicode.  Note that the buffer pointed to by "s" needs to be at
           least "UTF8_MAXBYTES_CASE+1" bytes since the titlecase version may
           be longer than the original character.

           The first code point of the titlecased version is returned (but
           note, as explained at the top of this section, that there may be
           more).

            UV  toTITLE_uvchr(UV cp, U8* s, STRLEN* lenp)

       "toUPPER"
           Converts the specified character to uppercase.  If the input is
           anything but an ASCII lowercase character, that input character
           itself is returned.  Variant "toUPPER_A" is equivalent.

            U8  toUPPER(int ch)

       "toUPPER_utf8"
       "toUPPER_utf8_safe"
           Converts the first UTF-8 encoded character in the sequence starting
           at "p" and extending no further than "e - 1" to its uppercase
           version, and stores that in UTF-8 in "s", and its length in bytes
           in "lenp".  Note that the buffer pointed to by "s" needs to be at
           least "UTF8_MAXBYTES_CASE+1" bytes since the uppercase version may
           be longer than the original character.

           The first code point of the uppercased version is returned (but
           note, as explained at the top of this section, that there may be
           more).

           It will not attempt to read beyond "e - 1", provided that the
           constraint "s < e" is true (this is asserted for in "-DDEBUGGING"
           builds).  If the UTF-8 for the input character is malformed in some
           way, the program may croak, or the function may return the
           REPLACEMENT CHARACTER, at the discretion of the implementation, and
           subject to change in future releases.

           "toUPPER_utf8_safe" is now just a different spelling of plain
           "toUPPER_utf8"

            UV  toUPPER_utf8(U8* p, U8* e, U8* s, STRLEN* lenp)

       "toUPPER_uvchr"
           Converts the code point "cp" to its uppercase version, and stores
           that in UTF-8 in "s", and its length in bytes in "lenp".  The code
           point is interpreted as native if less than 256; otherwise as
           Unicode.  Note that the buffer pointed to by "s" needs to be at
           least "UTF8_MAXBYTES_CASE+1" bytes since the uppercase version may
           be longer than the original character.

           The first code point of the uppercased version is returned (but
           note, as explained at the top of this section, that there may be
           more.)

            UV  toUPPER_uvchr(UV cp, U8* s, STRLEN* lenp)


Character classification

       This section is about functions (really macros) that classify
       characters into types, such as punctuation versus alphabetic, etc.
       Most of these are analogous to regular expression character classes.
       (See "POSIX Character Classes" in perlrecharclass.)  There are several
       variants for each class.  (Not all macros have all variants; each item
       below lists the ones valid for it.)  None are affected by "use bytes",
       and only the ones with "LC" in the name are affected by the current
       locale.

       The base function, e.g., "isALPHA()", takes any signed or unsigned
       value, treating it as a code point, and returns a boolean as to whether
       or not the character represented by it is (or on non-ASCII platforms,
       corresponds to) an ASCII character in the named class based on
       platform, Unicode, and Perl rules.  If the input is a number that
       doesn't fit in an octet, FALSE is returned.

       Variant "isFOO_A" (e.g., "isALPHA_A()") is identical to the base
       function with no suffix "_A".  This variant is used to emphasize by its
       name that only ASCII-range characters can return TRUE.

       Variant "isFOO_L1" imposes the Latin-1 (or EBCDIC equivalent) character
       set onto the platform.  That is, the code points that are ASCII are
       unaffected, since ASCII is a subset of Latin-1.  But the non-ASCII code
       points are treated as if they are Latin-1 characters.  For example,
       "isWORDCHAR_L1()" will return true when called with the code point
       0xDF, which is a word character in both ASCII and EBCDIC (though it
       represents different characters in each).  If the input is a number
       that doesn't fit in an octet, FALSE is returned.  (Perl's documentation
       uses a colloquial definition of Latin-1, to include all code points
       below 256.)

       Variant "isFOO_uvchr" is exactly like the "isFOO_L1" variant, for
       inputs below 256, but if the code point is larger than 255, Unicode
       rules are used to determine if it is in the character class.  For
       example, "isWORDCHAR_uvchr(0x100)" returns TRUE, since 0x100 is LATIN
       CAPITAL LETTER A WITH MACRON in Unicode, and is a word character.

       Variants "isFOO_utf8" and "isFOO_utf8_safe" are like "isFOO_uvchr", but
       are used for UTF-8 encoded strings.  The two forms are different names
       for the same thing.  Each call to one of these classifies the first
       character of the string starting at "p".  The second parameter, "e",
       points to anywhere in the string beyond the first character, up to one
       byte past the end of the entire string.  Although both variants are
       identical, the suffix "_safe" in one name emphasizes that it will not
       attempt to read beyond "e - 1", provided that the constraint "s < e" is
       true (this is asserted for in "-DDEBUGGING" builds).  If the UTF-8 for
       the input character is malformed in some way, the program may croak, or
       the function may return FALSE, at the discretion of the implementation,
       and subject to change in future releases.

       Variant "isFOO_LC" is like the "isFOO_A" and "isFOO_L1" variants, but
       the result is based on the current locale, which is what "LC" in the
       name stands for.  If Perl can determine that the current locale is a
       UTF-8 locale, it uses the published Unicode rules; otherwise, it uses
       the C library function that gives the named classification.  For
       example, "isDIGIT_LC()" when not in a UTF-8 locale returns the result
       of calling "isdigit()".  FALSE is always returned if the input won't
       fit into an octet.  On some platforms where the C library function is
       known to be defective, Perl changes its result to follow the POSIX
       standard's rules.

       Variant "isFOO_LC_uvchr" acts exactly like "isFOO_LC" for inputs less
       than 256, but for larger ones it returns the Unicode classification of
       the code point.

       Variants "isFOO_LC_utf8" and "isFOO_LC_utf8_safe" are like
       "isFOO_LC_uvchr", but are used for UTF-8 encoded strings.  The two
       forms are different names for the same thing.  Each call to one of
       these classifies the first character of the string starting at "p".
       The second parameter, "e", points to anywhere in the string beyond the
       first character, up to one byte past the end of the entire string.
       Although both variants are identical, the suffix "_safe" in one name
       emphasizes that it will not attempt to read beyond "e - 1", provided
       that the constraint "s < e" is true (this is asserted for in
       "-DDEBUGGING" builds).  If the UTF-8 for the input character is
       malformed in some way, the program may croak, or the function may
       return FALSE, at the discretion of the implementation, and subject to
       change in future releases.

       "isALPHA"
       "isALPHA_A"
       "isALPHA_L1"
       "isALPHA_uvchr"
       "isALPHA_utf8_safe"
       "isALPHA_utf8"
       "isALPHA_LC"
       "isALPHA_LC_uvchr"
       "isALPHA_LC_utf8_safe"
           Returns a boolean indicating whether the specified input is one of
           "[A-Za-z]", analogous to "m/[[:alpha:]]/".  See the top of this
           section for an explanation of the variants.

            bool  isALPHA             (UV ch)
            bool  isALPHA_A           (UV ch)
            bool  isALPHA_L1          (UV ch)
            bool  isALPHA_uvchr       (UV ch)
            bool  isALPHA_utf8_safe   (U8 * s, U8 * end)
            bool  isALPHA_utf8        (U8 * s, U8 * end)
            bool  isALPHA_LC          (UV ch)
            bool  isALPHA_LC_uvchr    (UV ch)
            bool  isALPHA_LC_utf8_safe(U8 * s, U8 *end)

       "isALPHANUMERIC"
       "isALPHANUMERIC_A"
       "isALPHANUMERIC_L1"
       "isALPHANUMERIC_uvchr"
       "isALPHANUMERIC_utf8_safe"
       "isALPHANUMERIC_utf8"
       "isALPHANUMERIC_LC"
       "isALPHANUMERIC_LC_uvchr"
       "isALPHANUMERIC_LC_utf8_safe"
       "isALNUMC"
       "isALNUMC_A"
       "isALNUMC_L1"
       "isALNUMC_LC"
       "isALNUMC_LC_uvchr"
           Returns a boolean indicating whether the specified character is one
           of "[A-Za-z0-9]", analogous to "m/[[:alnum:]]/".  See the top of
           this section for an explanation of the variants.

           A (discouraged from use) synonym is "isALNUMC" (where the "C"
           suffix means this corresponds to the C language alphanumeric
           definition).  Also there are the variants "isALNUMC_A",
           "isALNUMC_L1" "isALNUMC_LC", and "isALNUMC_LC_uvchr".

            bool  isALPHANUMERIC             (UV ch)
            bool  isALPHANUMERIC_A           (UV ch)
            bool  isALPHANUMERIC_L1          (UV ch)
            bool  isALPHANUMERIC_uvchr       (UV ch)
            bool  isALPHANUMERIC_utf8_safe   (U8 * s, U8 * end)
            bool  isALPHANUMERIC_utf8        (U8 * s, U8 * end)
            bool  isALPHANUMERIC_LC          (UV ch)
            bool  isALPHANUMERIC_LC_uvchr    (UV ch)
            bool  isALPHANUMERIC_LC_utf8_safe(U8 * s, U8 *end)
            bool  isALNUMC                   (UV ch)
            bool  isALNUMC_A                 (UV ch)
            bool  isALNUMC_L1                (UV ch)
            bool  isALNUMC_LC                (UV ch)
            bool  isALNUMC_LC_uvchr          (UV ch)

       "isASCII"
       "isASCII_A"
       "isASCII_L1"
       "isASCII_uvchr"
       "isASCII_utf8_safe"
       "isASCII_utf8"
       "isASCII_LC"
       "isASCII_LC_uvchr"
       "isASCII_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is one
           of the 128 characters in the ASCII character set, analogous to
           "m/[[:ascii:]]/".  On non-ASCII platforms, it returns TRUE iff this
           character corresponds to an ASCII character.  Variants
           "isASCII_A()" and "isASCII_L1()" are identical to "isASCII()".  See
           the top of this section for an explanation of the variants.  Note,
           however, that some platforms do not have the C library routine
           "isascii()".  In these cases, the variants whose names contain "LC"
           are the same as the corresponding ones without.

           Also note, that because all ASCII characters are UTF-8 invariant
           (meaning they have the exact same representation (always a single
           byte) whether encoded in UTF-8 or not), "isASCII" will give the
           correct results when called with any byte in any string encoded or
           not in UTF-8.  And similarly "isASCII_utf8" and "isASCII_utf8_safe"
           will work properly on any string encoded or not in UTF-8.

            bool  isASCII             (UV ch)
            bool  isASCII_A           (UV ch)
            bool  isASCII_L1          (UV ch)
            bool  isASCII_uvchr       (UV ch)
            bool  isASCII_utf8_safe   (U8 * s, U8 * end)
            bool  isASCII_utf8        (U8 * s, U8 * end)
            bool  isASCII_LC          (UV ch)
            bool  isASCII_LC_uvchr    (UV ch)
            bool  isASCII_LC_utf8_safe(U8 * s, U8 *end)

       "isBLANK"
       "isBLANK_A"
       "isBLANK_L1"
       "isBLANK_uvchr"
       "isBLANK_utf8_safe"
       "isBLANK_utf8"
       "isBLANK_LC"
       "isBLANK_LC_uvchr"
       "isBLANK_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           character considered to be a blank, analogous to "m/[[:blank:]]/".
           See the top of this section for an explanation of the variants.
           Note, however, that some platforms do not have the C library
           routine "isblank()".  In these cases, the variants whose names
           contain "LC" are the same as the corresponding ones without.

            bool  isBLANK             (UV ch)
            bool  isBLANK_A           (UV ch)
            bool  isBLANK_L1          (UV ch)
            bool  isBLANK_uvchr       (UV ch)
            bool  isBLANK_utf8_safe   (U8 * s, U8 * end)
            bool  isBLANK_utf8        (U8 * s, U8 * end)
            bool  isBLANK_LC          (UV ch)
            bool  isBLANK_LC_uvchr    (UV ch)
            bool  isBLANK_LC_utf8_safe(U8 * s, U8 *end)

       "isCNTRL"
       "isCNTRL_A"
       "isCNTRL_L1"
       "isCNTRL_uvchr"
       "isCNTRL_utf8_safe"
       "isCNTRL_utf8"
       "isCNTRL_LC"
       "isCNTRL_LC_uvchr"
       "isCNTRL_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           control character, analogous to "m/[[:cntrl:]]/".  See the top of
           this section for an explanation of the variants.  On EBCDIC
           platforms, you almost always want to use the "isCNTRL_L1" variant.

            bool  isCNTRL             (UV ch)
            bool  isCNTRL_A           (UV ch)
            bool  isCNTRL_L1          (UV ch)
            bool  isCNTRL_uvchr       (UV ch)
            bool  isCNTRL_utf8_safe   (U8 * s, U8 * end)
            bool  isCNTRL_utf8        (U8 * s, U8 * end)
            bool  isCNTRL_LC          (UV ch)
            bool  isCNTRL_LC_uvchr    (UV ch)
            bool  isCNTRL_LC_utf8_safe(U8 * s, U8 *end)

       "isDIGIT"
       "isDIGIT_A"
       "isDIGIT_L1"
       "isDIGIT_uvchr"
       "isDIGIT_utf8_safe"
       "isDIGIT_utf8"
       "isDIGIT_LC"
       "isDIGIT_LC_uvchr"
       "isDIGIT_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           digit, analogous to "m/[[:digit:]]/".  Variants "isDIGIT_A" and
           "isDIGIT_L1" are identical to "isDIGIT".  See the top of this
           section for an explanation of the variants.

            bool  isDIGIT             (UV ch)
            bool  isDIGIT_A           (UV ch)
            bool  isDIGIT_L1          (UV ch)
            bool  isDIGIT_uvchr       (UV ch)
            bool  isDIGIT_utf8_safe   (U8 * s, U8 * end)
            bool  isDIGIT_utf8        (U8 * s, U8 * end)
            bool  isDIGIT_LC          (UV ch)
            bool  isDIGIT_LC_uvchr    (UV ch)
            bool  isDIGIT_LC_utf8_safe(U8 * s, U8 *end)

       "isGRAPH"
       "isGRAPH_A"
       "isGRAPH_L1"
       "isGRAPH_uvchr"
       "isGRAPH_utf8_safe"
       "isGRAPH_utf8"
       "isGRAPH_LC"
       "isGRAPH_LC_uvchr"
       "isGRAPH_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           graphic character, analogous to "m/[[:graph:]]/".  See the top of
           this section for an explanation of the variants.

            bool  isGRAPH             (UV ch)
            bool  isGRAPH_A           (UV ch)
            bool  isGRAPH_L1          (UV ch)
            bool  isGRAPH_uvchr       (UV ch)
            bool  isGRAPH_utf8_safe   (U8 * s, U8 * end)
            bool  isGRAPH_utf8        (U8 * s, U8 * end)
            bool  isGRAPH_LC          (UV ch)
            bool  isGRAPH_LC_uvchr    (UV ch)
            bool  isGRAPH_LC_utf8_safe(U8 * s, U8 *end)

       "isIDCONT"
       "isIDCONT_A"
       "isIDCONT_L1"
       "isIDCONT_uvchr"
       "isIDCONT_utf8_safe"
       "isIDCONT_utf8"
       "isIDCONT_LC"
       "isIDCONT_LC_uvchr"
       "isIDCONT_LC_utf8_safe"
           Returns a boolean indicating whether the specified character can be
           the second or succeeding character of an identifier.  This is very
           close to, but not quite the same as the official Unicode property
           "XID_Continue".  The difference is that this returns true only if
           the input character also matches "isWORDCHAR".  See the top of this
           section for an explanation of the variants.

            bool  isIDCONT             (UV ch)
            bool  isIDCONT_A           (UV ch)
            bool  isIDCONT_L1          (UV ch)
            bool  isIDCONT_uvchr       (UV ch)
            bool  isIDCONT_utf8_safe   (U8 * s, U8 * end)
            bool  isIDCONT_utf8        (U8 * s, U8 * end)
            bool  isIDCONT_LC          (UV ch)
            bool  isIDCONT_LC_uvchr    (UV ch)
            bool  isIDCONT_LC_utf8_safe(U8 * s, U8 *end)

       "isIDFIRST"
       "isIDFIRST_A"
       "isIDFIRST_L1"
       "isIDFIRST_uvchr"
       "isIDFIRST_utf8_safe"
       "isIDFIRST_utf8"
       "isIDFIRST_LC"
       "isIDFIRST_LC_uvchr"
       "isIDFIRST_LC_utf8_safe"
           Returns a boolean indicating whether the specified character can be
           the first character of an identifier.  This is very close to, but
           not quite the same as the official Unicode property "XID_Start".
           The difference is that this returns true only if the input
           character also matches "isWORDCHAR".  See the top of this section
           for an explanation of the variants.

            bool  isIDFIRST             (UV ch)
            bool  isIDFIRST_A           (UV ch)
            bool  isIDFIRST_L1          (UV ch)
            bool  isIDFIRST_uvchr       (UV ch)
            bool  isIDFIRST_utf8_safe   (U8 * s, U8 * end)
            bool  isIDFIRST_utf8        (U8 * s, U8 * end)
            bool  isIDFIRST_LC          (UV ch)
            bool  isIDFIRST_LC_uvchr    (UV ch)
            bool  isIDFIRST_LC_utf8_safe(U8 * s, U8 *end)

       "isLOWER"
       "isLOWER_A"
       "isLOWER_L1"
       "isLOWER_uvchr"
       "isLOWER_utf8_safe"
       "isLOWER_utf8"
       "isLOWER_LC"
       "isLOWER_LC_uvchr"
       "isLOWER_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           lowercase character, analogous to "m/[[:lower:]]/".  See the top of
           this section for an explanation of the variants

            bool  isLOWER             (UV ch)
            bool  isLOWER_A           (UV ch)
            bool  isLOWER_L1          (UV ch)
            bool  isLOWER_uvchr       (UV ch)
            bool  isLOWER_utf8_safe   (U8 * s, U8 * end)
            bool  isLOWER_utf8        (U8 * s, U8 * end)
            bool  isLOWER_LC          (UV ch)
            bool  isLOWER_LC_uvchr    (UV ch)
            bool  isLOWER_LC_utf8_safe(U8 * s, U8 *end)

       "isOCTAL"
       "isOCTAL_A"
       "isOCTAL_L1"
           Returns a boolean indicating whether the specified character is an
           octal digit, [0-7].  The only two variants are "isOCTAL_A" and
           "isOCTAL_L1"; each is identical to "isOCTAL".

            bool  isOCTAL(UV ch)

       "isPRINT"
       "isPRINT_A"
       "isPRINT_L1"
       "isPRINT_uvchr"
       "isPRINT_utf8_safe"
       "isPRINT_utf8"
       "isPRINT_LC"
       "isPRINT_LC_uvchr"
       "isPRINT_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           printable character, analogous to "m/[[:print:]]/".  See the top of
           this section for an explanation of the variants.

            bool  isPRINT             (UV ch)
            bool  isPRINT_A           (UV ch)
            bool  isPRINT_L1          (UV ch)
            bool  isPRINT_uvchr       (UV ch)
            bool  isPRINT_utf8_safe   (U8 * s, U8 * end)
            bool  isPRINT_utf8        (U8 * s, U8 * end)
            bool  isPRINT_LC          (UV ch)
            bool  isPRINT_LC_uvchr    (UV ch)
            bool  isPRINT_LC_utf8_safe(U8 * s, U8 *end)

       "isPSXSPC"
       "isPSXSPC_A"
       "isPSXSPC_L1"
       "isPSXSPC_uvchr"
       "isPSXSPC_utf8_safe"
       "isPSXSPC_utf8"
       "isPSXSPC_LC"
       "isPSXSPC_LC_uvchr"
       "isPSXSPC_LC_utf8_safe"
           (short for Posix Space) Starting in 5.18, this is identical in all
           its forms to the corresponding "isSPACE()" macros.  The locale
           forms of this macro are identical to their corresponding
           "isSPACE()" forms in all Perl releases.  In releases prior to 5.18,
           the non-locale forms differ from their "isSPACE()" forms only in
           that the "isSPACE()" forms don't match a Vertical Tab, and the
           "isPSXSPC()" forms do.  Otherwise they are identical.  Thus this
           macro is analogous to what "m/[[:space:]]/" matches in a regular
           expression.  See the top of this section for an explanation of the
           variants.

            bool  isPSXSPC             (UV ch)
            bool  isPSXSPC_A           (UV ch)
            bool  isPSXSPC_L1          (UV ch)
            bool  isPSXSPC_uvchr       (UV ch)
            bool  isPSXSPC_utf8_safe   (U8 * s, U8 * end)
            bool  isPSXSPC_utf8        (U8 * s, U8 * end)
            bool  isPSXSPC_LC          (UV ch)
            bool  isPSXSPC_LC_uvchr    (UV ch)
            bool  isPSXSPC_LC_utf8_safe(U8 * s, U8 *end)

       "isPUNCT"
       "isPUNCT_A"
       "isPUNCT_L1"
       "isPUNCT_uvchr"
       "isPUNCT_utf8_safe"
       "isPUNCT_utf8"
       "isPUNCT_LC"
       "isPUNCT_LC_uvchr"
       "isPUNCT_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           punctuation character, analogous to "m/[[:punct:]]/".  Note that
           the definition of what is punctuation isn't as straightforward as
           one might desire.  See "POSIX Character Classes" in perlrecharclass
           for details.  See the top of this section for an explanation of the
           variants.

            bool  isPUNCT             (UV ch)
            bool  isPUNCT_A           (UV ch)
            bool  isPUNCT_L1          (UV ch)
            bool  isPUNCT_uvchr       (UV ch)
            bool  isPUNCT_utf8_safe   (U8 * s, U8 * end)
            bool  isPUNCT_utf8        (U8 * s, U8 * end)
            bool  isPUNCT_LC          (UV ch)
            bool  isPUNCT_LC_uvchr    (UV ch)
            bool  isPUNCT_LC_utf8_safe(U8 * s, U8 *end)

       "isSPACE"
       "isSPACE_A"
       "isSPACE_L1"
       "isSPACE_uvchr"
       "isSPACE_utf8_safe"
       "isSPACE_utf8"
       "isSPACE_LC"
       "isSPACE_LC_uvchr"
       "isSPACE_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           whitespace character.  This is analogous to what "m/\s/" matches in
           a regular expression.  Starting in Perl 5.18 this also matches what
           "m/[[:space:]]/" does.  Prior to 5.18, only the locale forms of
           this macro (the ones with "LC" in their names) matched precisely
           what "m/[[:space:]]/" does.  In those releases, the only
           difference, in the non-locale variants, was that "isSPACE()" did
           not match a vertical tab.  (See "isPSXSPC" for a macro that matches
           a vertical tab in all releases.)  See the top of this section for
           an explanation of the variants.

            bool  isSPACE             (UV ch)
            bool  isSPACE_A           (UV ch)
            bool  isSPACE_L1          (UV ch)
            bool  isSPACE_uvchr       (UV ch)
            bool  isSPACE_utf8_safe   (U8 * s, U8 * end)
            bool  isSPACE_utf8        (U8 * s, U8 * end)
            bool  isSPACE_LC          (UV ch)
            bool  isSPACE_LC_uvchr    (UV ch)
            bool  isSPACE_LC_utf8_safe(U8 * s, U8 *end)

       "isUPPER"
       "isUPPER_A"
       "isUPPER_L1"
       "isUPPER_uvchr"
       "isUPPER_utf8_safe"
       "isUPPER_utf8"
       "isUPPER_LC"
       "isUPPER_LC_uvchr"
       "isUPPER_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is an
           uppercase character, analogous to "m/[[:upper:]]/".  See the top of
           this section for an explanation of the variants.

            bool  isUPPER             (UV ch)
            bool  isUPPER_A           (UV ch)
            bool  isUPPER_L1          (UV ch)
            bool  isUPPER_uvchr       (UV ch)
            bool  isUPPER_utf8_safe   (U8 * s, U8 * end)
            bool  isUPPER_utf8        (U8 * s, U8 * end)
            bool  isUPPER_LC          (UV ch)
            bool  isUPPER_LC_uvchr    (UV ch)
            bool  isUPPER_LC_utf8_safe(U8 * s, U8 *end)

       "isWORDCHAR"
       "isWORDCHAR_A"
       "isWORDCHAR_L1"
       "isWORDCHAR_uvchr"
       "isWORDCHAR_utf8_safe"
       "isWORDCHAR_utf8"
       "isWORDCHAR_LC"
       "isWORDCHAR_LC_uvchr"
       "isWORDCHAR_LC_utf8_safe"
       "isALNUM"
       "isALNUM_A"
       "isALNUM_LC"
       "isALNUM_LC_uvchr"
           Returns a boolean indicating whether the specified character is a
           character that is a word character, analogous to what "m/\w/" and
           "m/[[:word:]]/" match in a regular expression.  A word character is
           an alphabetic character, a decimal digit, a connecting punctuation
           character (such as an underscore), or a "mark" character that
           attaches to one of those (like some sort of accent).  "isALNUM()"
           is a synonym provided for backward compatibility, even though a
           word character includes more than the standard C language meaning
           of alphanumeric.  See the top of this section for an explanation of
           the variants.  "isWORDCHAR_A", "isWORDCHAR_L1", "isWORDCHAR_uvchr",
           "isWORDCHAR_LC", "isWORDCHAR_LC_uvchr", "isWORDCHAR_LC_utf8", and
           "isWORDCHAR_LC_utf8_safe" are also as described there, but
           additionally include the platform's native underscore.

            bool  isWORDCHAR             (UV ch)
            bool  isWORDCHAR_A           (UV ch)
            bool  isWORDCHAR_L1          (UV ch)
            bool  isWORDCHAR_uvchr       (UV ch)
            bool  isWORDCHAR_utf8_safe   (U8 * s, U8 * end)
            bool  isWORDCHAR_utf8        (U8 * s, U8 * end)
            bool  isWORDCHAR_LC          (UV ch)
            bool  isWORDCHAR_LC_uvchr    (UV ch)
            bool  isWORDCHAR_LC_utf8_safe(U8 * s, U8 *end)
            bool  isALNUM                (UV ch)
            bool  isALNUM_A              (UV ch)
            bool  isALNUM_LC             (UV ch)
            bool  isALNUM_LC_uvchr       (UV ch)

       "isXDIGIT"
       "isXDIGIT_A"
       "isXDIGIT_L1"
       "isXDIGIT_uvchr"
       "isXDIGIT_utf8_safe"
       "isXDIGIT_utf8"
       "isXDIGIT_LC"
       "isXDIGIT_LC_uvchr"
       "isXDIGIT_LC_utf8_safe"
           Returns a boolean indicating whether the specified character is a
           hexadecimal digit.  In the ASCII range these are "[0-9A-Fa-f]".
           Variants "isXDIGIT_A()" and "isXDIGIT_L1()" are identical to
           "isXDIGIT()".  See the top of this section for an explanation of
           the variants.

            bool  isXDIGIT             (UV ch)
            bool  isXDIGIT_A           (UV ch)
            bool  isXDIGIT_L1          (UV ch)
            bool  isXDIGIT_uvchr       (UV ch)
            bool  isXDIGIT_utf8_safe   (U8 * s, U8 * end)
            bool  isXDIGIT_utf8        (U8 * s, U8 * end)
            bool  isXDIGIT_LC          (UV ch)
            bool  isXDIGIT_LC_uvchr    (UV ch)
            bool  isXDIGIT_LC_utf8_safe(U8 * s, U8 *end)


Compiler and Preprocessor information

       "CPPLAST"
           This symbol is intended to be used along with "CPPRUN" in the same
           manner symbol "CPPMINUS" is used with "CPPSTDIN". It contains
           either "-" or "".

       "CPPMINUS"
           This symbol contains the second part of the string which will
           invoke the C preprocessor on the standard input and produce to
           standard output.  This symbol will have the value "-" if "CPPSTDIN"
           needs a minus to specify standard input, otherwise the value is "".

       "CPPRUN"
           This symbol contains the string which will invoke a C preprocessor
           on the standard input and produce to standard output. It needs to
           end with "CPPLAST", after all other preprocessor flags have been
           specified.  The main difference with "CPPSTDIN" is that this
           program will never be a pointer to a shell wrapper, i.e. it will be
           empty if no preprocessor is available directly to the user. Note
           that it may well be different from the preprocessor used to compile
           the C program.

       "CPPSTDIN"
           This symbol contains the first part of the string which will invoke
           the C preprocessor on the standard input and produce to standard
           output.  Typical value of "cc -E" or "/lib/cpp", but it can also
           call a wrapper. See "CPPRUN".

       "HASATTRIBUTE_ALWAYS_INLINE"
           Can we handle "GCC" attribute for functions that should always be
           inlined.

       "HASATTRIBUTE_DEPRECATED"
           Can we handle "GCC" attribute for marking deprecated "APIs"

       "HASATTRIBUTE_FORMAT"
           Can we handle "GCC" attribute for checking printf-style formats

       "HASATTRIBUTE_NONNULL"
           Can we handle "GCC" attribute for nonnull function parms.

       "HASATTRIBUTE_NORETURN"
           Can we handle "GCC" attribute for functions that do not return

       "HASATTRIBUTE_PURE"
           Can we handle "GCC" attribute for pure functions

       "HASATTRIBUTE_UNUSED"
           Can we handle "GCC" attribute for unused variables and arguments

       "HASATTRIBUTE_WARN_UNUSED_RESULT"
           Can we handle "GCC" attribute for warning on unused results

       "HAS_BUILTIN_ADD_OVERFLOW"
           This symbol, if defined, indicates that the compiler supports
           "__builtin_add_overflow" for adding integers with overflow checks.

       "HAS_BUILTIN_CHOOSE_EXPR"
           Can we handle "GCC" builtin for compile-time ternary-like
           expressions

       "HAS_BUILTIN_EXPECT"
           Can we handle "GCC" builtin for telling that certain values are
           more likely

       "HAS_BUILTIN_MUL_OVERFLOW"
           This symbol, if defined, indicates that the compiler supports
           "__builtin_mul_overflow" for multiplying integers with overflow
           checks.

       "HAS_BUILTIN_SUB_OVERFLOW"
           This symbol, if defined, indicates that the compiler supports
           "__builtin_sub_overflow" for subtracting integers with overflow
           checks.

       "HAS_C99_VARIADIC_MACROS"
           If defined, the compiler supports C99 variadic macros.

       "HAS_STATIC_INLINE"
           This symbol, if defined, indicates that the C compiler supports
           C99-style static inline.  That is, the function can't be called
           from another translation unit.

       "MEM_ALIGNBYTES"
           This symbol contains the number of bytes required to align a
           double, or a long double when applicable. Usual values are 2, 4 and
           8. The default is eight, for safety.  For cross-compiling or
           multiarch support, Configure will set a minimum of 8.

       "PERL_STATIC_INLINE"
           This symbol gives the best-guess incantation to use for static
           inline functions.  If "HAS_STATIC_INLINE" is defined, this will
           give C99-style inline.  If "HAS_STATIC_INLINE" is not defined, this
           will give a plain 'static'.  It will always be defined to something
           that gives static linkage.  Possibilities include

            static inline       (c99)
            static __inline__   (gcc -ansi)
            static __inline     (MSVC)
            static _inline      (older MSVC)
            static              (c89 compilers)

       "U32_ALIGNMENT_REQUIRED"
           This symbol, if defined, indicates that you must access character
           data through U32-aligned pointers.


Compiler directives

       "ASSUME"
           "ASSUME" is like "assert()", but it has a benefit in a release
           build. It is a hint to a compiler about a statement of fact in a
           function call free expression, which allows the compiler to
           generate better machine code.  In a debug build, ASSUME(x) is a
           synonym for assert(x). ASSUME(0) means the control path is
           unreachable. In a for loop, "ASSUME" can be used to hint that a
           loop will run at least X times. "ASSUME" is based off MSVC's
           "__assume" intrinsic function, see its documents for more details.

              ASSUME(bool expr)

       "dNOOP"
           Declare nothing; typically used as a placeholder to replace
           something that used to declare something.  Works on compilers that
           require declarations before any code.

              dNOOP;

       "END_EXTERN_C"
           When not compiling using C++, expands to nothing.  Otherwise ends a
           section of code already begun by a "START_EXTERN_C".

              END_EXTERN_C

       "EXTERN_C"
           When not compiling using C++, expands to nothing.  Otherwise is
           used in a declaration of a function to indicate the function should
           have external C linkage.  This is required for things to work for
           just about all functions with external linkage compiled into perl.
           Often, you can use "START_EXTERN_C" ... "END_EXTERN_C" blocks
           surrounding all your code that you need to have this linkage.

           Example usage:

            EXTERN_C int flock(int fd, int op);

       "LIKELY"
           Returns the input unchanged, but at the same time it gives a branch
           prediction hint to the compiler that this condition is likely to be
           true.

              LIKELY(bool expr)

       "NOOP"
           Do nothing; typically used as a placeholder to replace something
           that used to do something.

              NOOP;

       "PERL_UNUSED_ARG"
           This is used to suppress compiler warnings that a parameter to a
           function is not used.  This situation can arise, for example, when
           a parameter is needed under some configuration conditions, but not
           others, so that C preprocessor conditional compilation causes it be
           used just some times.

              PERL_UNUSED_ARG(void x);

       "PERL_UNUSED_CONTEXT"
           This is used to suppress compiler warnings that the thread context
           parameter to a function is not used.  This situation can arise, for
           example, when a C preprocessor conditional compilation causes it be
           used just some times.

              PERL_UNUSED_CONTEXT;

       "PERL_UNUSED_DECL"
           Tells the compiler that the parameter in the function prototype
           just before it is not necessarily expected to be used in the
           function.  Not that many compilers understand this, so this should
           only be used in cases where "PERL_UNUSED_ARG" can't conveniently be
           used.

           Example usage:

            Signal_t
            Perl_perly_sighandler(int sig, Siginfo_t *sip PERL_UNUSED_DECL,
                                  void *uap PERL_UNUSED_DECL, bool safe)

       "PERL_UNUSED_RESULT"
           This macro indicates to discard the return value of the function
           call inside it, e.g.,

            PERL_UNUSED_RESULT(foo(a, b))

           The main reason for this is that the combination of "gcc
           -Wunused-result" (part of "-Wall") and the
           "__attribute__((warn_unused_result))" cannot be silenced with
           casting to "void".  This causes trouble when the system header
           files use the attribute.

           Use "PERL_UNUSED_RESULT" sparingly, though, since usually the
           warning is there for a good reason: you might lose success/failure
           information, or leak resources, or changes in resources.

           But sometimes you just want to ignore the return value, e.g., on
           codepaths soon ending up in abort, or in "best effort" attempts, or
           in situations where there is no good way to handle failures.

           Sometimes "PERL_UNUSED_RESULT" might not be the most natural way:
           another possibility is that you can capture the return value and
           use "PERL_UNUSED_VAR" on that.

              PERL_UNUSED_RESULT(void x)

       "PERL_UNUSED_VAR"
           This is used to suppress compiler warnings that the variable x is
           not used.  This situation can arise, for example, when a C
           preprocessor conditional compilation causes it be used just some
           times.

              PERL_UNUSED_VAR(void x);

       "PERL_USE_GCC_BRACE_GROUPS"
           This C pre-processor value, if defined, indicates that it is
           permissible to use the GCC brace groups extension.  This extension,
           of the form

            ({ statement ... })

           turns the block consisting of statements ... into an expression
           with a value, unlike plain C language blocks.  This can present
           optimization possibilities, BUT you generally need to specify an
           alternative in case this ability doesn't exist or has otherwise
           been forbidden.

           Example usage:

            #ifdef PERL_USE_GCC_BRACE_GROUPS
              ...
            #else
              ...
            #endif

       "START_EXTERN_C"
           When not compiling using C++, expands to nothing.  Otherwise begins
           a section of code in which every function will effectively have
           "EXTERN_C" applied to it, that is to have external C linkage.  The
           section is ended by a "END_EXTERN_C".

              START_EXTERN_C

       "STATIC"
           Described in perlguts.

       "STMT_START"
       "STMT_END"
           This allows a series of statements in a macro to be used as a
           single statement, as in

            if (x) STMT_START { ... } STMT_END else ...

           Note that you can't return a value out of them, which limits their
           utility.  But see "PERL_USE_GCC_BRACE_GROUPS".

       "UNLIKELY"
           Returns the input unchanged, but at the same time it gives a branch
           prediction hint to the compiler that this condition is likely to be
           false.

              UNLIKELY(bool expr)

       "__ASSERT_"
           This is a helper macro to avoid preprocessor issues, replaced by
           nothing unless under DEBUGGING, where it expands to an assert of
           its argument, followed by a comma (hence the comma operator).  If
           we just used a straight assert(), we would get a comma with nothing
           before it when not DEBUGGING.

              __ASSERT_(bool expr)


Compile-time scope hooks

       "BhkDISABLE"
           NOTE: "BhkDISABLE" is experimental and may change or be removed
           without notice.

           Temporarily disable an entry in this BHK structure, by clearing the
           appropriate flag.  "which" is a preprocessor token indicating which
           entry to disable.

            void  BhkDISABLE(BHK *hk, which)

       "BhkENABLE"
           NOTE: "BhkENABLE" is experimental and may change or be removed
           without notice.

           Re-enable an entry in this BHK structure, by setting the
           appropriate flag.  "which" is a preprocessor token indicating which
           entry to enable.  This will assert (under -DDEBUGGING) if the entry
           doesn't contain a valid pointer.

            void  BhkENABLE(BHK *hk, which)

       "BhkENTRY_set"
           NOTE: "BhkENTRY_set" is experimental and may change or be removed
           without notice.

           Set an entry in the BHK structure, and set the flags to indicate it
           is valid.  "which" is a preprocessing token indicating which entry
           to set.  The type of "ptr" depends on the entry.

            void  BhkENTRY_set(BHK *hk, which, void *ptr)

       "blockhook_register"
           NOTE: "blockhook_register" is experimental and may change or be
           removed without notice.

           Register a set of hooks to be called when the Perl lexical scope
           changes at compile time.  See "Compile-time scope hooks" in
           perlguts.

           NOTE: "blockhook_register" must be explicitly called as
           "Perl_blockhook_register" with an "aTHX_" parameter.

            void  Perl_blockhook_register(pTHX_ BHK *hk)


Concurrency

       "aTHX"
           Described in perlguts.

       "aTHX_"
           Described in perlguts.

       "CPERLscope"
           "DEPRECATED!"  It is planned to remove "CPERLscope" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Now a no-op.

            void  CPERLscope(void x)

       "dTHR"
           Described in perlguts.

       "dTHX"
           Described in perlguts.

       "dTHXa"
           On threaded perls, set "pTHX" to "a"; on unthreaded perls, do
           nothing

       "dTHXoa"
           Now a synonym for "dTHXa".

       "dVAR"
           This is now a synonym for dNOOP: declare nothing

       "GETENV_PRESERVES_OTHER_THREAD"
           This symbol, if defined, indicates that the getenv system call
           doesn't zap the static buffer of "getenv()" in a different thread.
           The typical "getenv()" implementation will return a pointer to the
           proper position in **environ.  But some may instead copy them to a
           static buffer in "getenv()".  If there is a per-thread instance of
           that buffer, or the return points to **environ, then a
           many-reader/1-writer mutex will work; otherwise an exclusive
           locking mutex is required to prevent races.

       "HAS_PTHREAD_ATFORK"
           This symbol, if defined, indicates that the "pthread_atfork"
           routine is available to setup fork handlers.

       "HAS_PTHREAD_ATTR_SETSCOPE"
           This symbol, if defined, indicates that the "pthread_attr_setscope"
           system call is available to set the contention scope attribute of a
           thread attribute object.

       "HAS_PTHREAD_YIELD"
           This symbol, if defined, indicates that the "pthread_yield" routine
           is available to yield the execution of the current thread.
           "sched_yield" is preferable to "pthread_yield".

       "HAS_SCHED_YIELD"
           This symbol, if defined, indicates that the "sched_yield" routine
           is available to yield the execution of the current thread.
           "sched_yield" is preferable to "pthread_yield".

       "I_MACH_CTHREADS"
           This symbol, if defined, indicates to the C program that it should
           include mach/cthreads.h.

            #ifdef I_MACH_CTHREADS
                #include <mach_cthreads.h>
            #endif

       "I_PTHREAD"
           This symbol, if defined, indicates to the C program that it should
           include pthread.h.

            #ifdef I_PTHREAD
                #include <pthread.h>
            #endif

       "MULTIPLICITY"
           This symbol, if defined, indicates that Perl should be built to use
           multiplicity.

       "OLD_PTHREADS_API"
           This symbol, if defined, indicates that Perl should be built to use
           the old draft "POSIX" threads "API".

       "OLD_PTHREAD_CREATE_JOINABLE"
           This symbol, if defined, indicates how to create pthread in
           joinable (aka undetached) state.  "NOTE": not defined if pthread.h
           already has defined "PTHREAD_CREATE_JOINABLE" (the new version of
           the constant).  If defined, known values are
           "PTHREAD_CREATE_UNDETACHED" and "__UNDETACHED".

       "pTHX"
           Described in perlguts.

       "pTHX_"
           Described in perlguts.

       "SCHED_YIELD"
           This symbol defines the way to yield the execution of the current
           thread.  Known ways are "sched_yield", "pthread_yield", and
           "pthread_yield" with "NULL".

       "SVf"
           Described in perlguts.

       "SVfARG"
           Described in perlguts.

              SVfARG(SV *sv)


COP Hint Hashes

       "cop_fetch_label"
           NOTE: "cop_fetch_label" is experimental and may change or be
           removed without notice.

           Returns the label attached to a cop, and stores its length in bytes
           into *len.  Upon return, *flags will be set to either "SVf_UTF8" or
           0.

           Alternatively, use the macro "CopLABEL_len_flags"; or if you don't
           need to know if the label is UTF-8 or not, the macro
           "CopLABEL_len"; or if you additionally dont need to know the
           length, "CopLABEL".

            const char *  cop_fetch_label(COP *const cop, STRLEN *len,
                                          U32 *flags)

       "CopFILE"
           Returns the name of the file associated with the "COP" "c"

            const char *  CopFILE(const COP * c)

       "CopFILEAV"
           Returns the AV associated with the "COP" "c"

            AV *  CopFILEAV(const COP * c)

       "CopFILEGV"
           Returns the GV associated with the "COP" "c"

            GV *  CopFILEGV(const COP * c)

       "CopFILEGV_set"
           Available only on unthreaded perls.  Makes "pv" the name of the
           file associated with the "COP" "c"

            void  CopFILEGV_set(COP * c, GV * gv)

       "CopFILE_set"
           Makes "pv" the name of the file associated with the "COP" "c"

            void  CopFILE_set(COP * c, const char * pv)

       "CopFILESV"
           Returns the SV associated with the "COP" "c"

            SV *  CopFILESV(const COP * c)

       "cophh_2hv"
           NOTE: "cophh_2hv" is experimental and may change or be removed
           without notice.

           Generates and returns a standard Perl hash representing the full
           set of key/value pairs in the cop hints hash "cophh".  "flags" is
           currently unused and must be zero.

            HV *  cophh_2hv(const COPHH *cophh, U32 flags)

       "cophh_copy"
           NOTE: "cophh_copy" is experimental and may change or be removed
           without notice.

           Make and return a complete copy of the cop hints hash "cophh".

            COPHH *  cophh_copy(COPHH *cophh)

       "cophh_delete_pv"
           NOTE: "cophh_delete_pv" is experimental and may change or be
           removed without notice.

           Like "cophh_delete_pvn", but takes a nul-terminated string instead
           of a string/length pair.

            COPHH *  cophh_delete_pv(COPHH *cophh, char *key, U32 hash,
                                     U32 flags)

       "cophh_delete_pvn"
           NOTE: "cophh_delete_pvn" is experimental and may change or be
           removed without notice.

           Delete a key and its associated value from the cop hints hash
           "cophh", and returns the modified hash.  The returned hash pointer
           is in general not the same as the hash pointer that was passed in.
           The input hash is consumed by the function, and the pointer to it
           must not be subsequently used.  Use "cophh_copy" if you need both
           hashes.

           The key is specified by "keypv" and "keylen".  If "flags" has the
           "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8,
           otherwise they are interpreted as Latin-1.  "hash" is a precomputed
           hash of the key string, or zero if it has not been precomputed.

            COPHH *  cophh_delete_pvn(COPHH *cophh, const char *keypv,
                                      STRLEN keylen, U32 hash, U32 flags)

       "cophh_delete_pvs"
           NOTE: "cophh_delete_pvs" is experimental and may change or be
           removed without notice.

           Like "cophh_delete_pvn", but takes a literal string instead of a
           string/length pair, and no precomputed hash.

            COPHH *  cophh_delete_pvs(COPHH *cophh, "key", U32 flags)

       "cophh_delete_sv"
           NOTE: "cophh_delete_sv" is experimental and may change or be
           removed without notice.

           Like "cophh_delete_pvn", but takes a Perl scalar instead of a
           string/length pair.

            COPHH *  cophh_delete_sv(COPHH *cophh, SV *key, U32 hash,
                                     U32 flags)

       "cophh_exists_pv"
           NOTE: "cophh_exists_pv" is experimental and may change or be
           removed without notice.

           Like "cophh_exists_pvn", but takes a nul-terminated string instead
           of a string/length pair.

            bool  cophh_exists_pv(const COPHH *cophh, const char *key,
                                  U32 hash, U32 flags)

       "cophh_exists_pvn"
           NOTE: "cophh_exists_pvn" is experimental and may change or be
           removed without notice.

           Look up the entry in the cop hints hash "cophh" with the key
           specified by "keypv" and "keylen".  If "flags" has the
           "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8,
           otherwise they are interpreted as Latin-1.  "hash" is a precomputed
           hash of the key string, or zero if it has not been precomputed.
           Returns true if a value exists, and false otherwise.

            bool  cophh_exists_pvn(const COPHH *cophh, const char *keypv,
                                   STRLEN keylen, U32 hash, U32 flags)

       "cophh_exists_pvs"
           NOTE: "cophh_exists_pvs" is experimental and may change or be
           removed without notice.

           Like "cophh_exists_pvn", but takes a literal string instead of a
           string/length pair, and no precomputed hash.

            bool  cophh_exists_pvs(const COPHH *cophh, "key", U32 flags)

       "cophh_exists_sv"
           NOTE: "cophh_exists_sv" is experimental and may change or be
           removed without notice.

           Like "cophh_exists_pvn", but takes a Perl scalar instead of a
           string/length pair.

            bool  cophh_exists_sv(const COPHH *cophh, SV *key, U32 hash,
                                  U32 flags)

       "cophh_fetch_pv"
           NOTE: "cophh_fetch_pv" is experimental and may change or be removed
           without notice.

           Like "cophh_fetch_pvn", but takes a nul-terminated string instead
           of a string/length pair.

            SV *  cophh_fetch_pv(const COPHH *cophh, const char *key,
                                 U32 hash, U32 flags)

       "cophh_fetch_pvn"
           NOTE: "cophh_fetch_pvn" is experimental and may change or be
           removed without notice.

           Look up the entry in the cop hints hash "cophh" with the key
           specified by "keypv" and "keylen".  If "flags" has the
           "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8,
           otherwise they are interpreted as Latin-1.  "hash" is a precomputed
           hash of the key string, or zero if it has not been precomputed.
           Returns a mortal scalar copy of the value associated with the key,
           or &PL_sv_placeholder if there is no value associated with the key.

            SV *  cophh_fetch_pvn(const COPHH *cophh, const char *keypv,
                                  STRLEN keylen, U32 hash, U32 flags)

       "cophh_fetch_pvs"
           NOTE: "cophh_fetch_pvs" is experimental and may change or be
           removed without notice.

           Like "cophh_fetch_pvn", but takes a literal string instead of a
           string/length pair, and no precomputed hash.

            SV *  cophh_fetch_pvs(const COPHH *cophh, "key", U32 flags)

       "cophh_fetch_sv"
           NOTE: "cophh_fetch_sv" is experimental and may change or be removed
           without notice.

           Like "cophh_fetch_pvn", but takes a Perl scalar instead of a
           string/length pair.

            SV *  cophh_fetch_sv(const COPHH *cophh, SV *key, U32 hash,
                                 U32 flags)

       "cophh_free"
           NOTE: "cophh_free" is experimental and may change or be removed
           without notice.

           Discard the cop hints hash "cophh", freeing all resources
           associated with it.

            void  cophh_free(COPHH *cophh)

       "cophh_new_empty"
           NOTE: "cophh_new_empty" is experimental and may change or be
           removed without notice.

           Generate and return a fresh cop hints hash containing no entries.

            COPHH *  cophh_new_empty()

       "cophh_store_pv"
           NOTE: "cophh_store_pv" is experimental and may change or be removed
           without notice.

           Like "cophh_store_pvn", but takes a nul-terminated string instead
           of a string/length pair.

            COPHH *  cophh_store_pv(COPHH *cophh, const char *key, U32 hash,
                                    SV *value, U32 flags)

       "cophh_store_pvn"
           NOTE: "cophh_store_pvn" is experimental and may change or be
           removed without notice.

           Stores a value, associated with a key, in the cop hints hash
           "cophh", and returns the modified hash.  The returned hash pointer
           is in general not the same as the hash pointer that was passed in.
           The input hash is consumed by the function, and the pointer to it
           must not be subsequently used.  Use "cophh_copy" if you need both
           hashes.

           The key is specified by "keypv" and "keylen".  If "flags" has the
           "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8,
           otherwise they are interpreted as Latin-1.  "hash" is a precomputed
           hash of the key string, or zero if it has not been precomputed.

           "value" is the scalar value to store for this key.  "value" is
           copied by this function, which thus does not take ownership of any
           reference to it, and later changes to the scalar will not be
           reflected in the value visible in the cop hints hash.  Complex
           types of scalar will not be stored with referential integrity, but
           will be coerced to strings.

            COPHH *  cophh_store_pvn(COPHH *cophh, const char *keypv,
                                     STRLEN keylen, U32 hash, SV *value,
                                     U32 flags)

       "cophh_store_pvs"
           NOTE: "cophh_store_pvs" is experimental and may change or be
           removed without notice.

           Like "cophh_store_pvn", but takes a literal string instead of a
           string/length pair, and no precomputed hash.

            COPHH *  cophh_store_pvs(COPHH *cophh, "key", SV *value,
                                     U32 flags)

       "cophh_store_sv"
           NOTE: "cophh_store_sv" is experimental and may change or be removed
           without notice.

           Like "cophh_store_pvn", but takes a Perl scalar instead of a
           string/length pair.

            COPHH *  cophh_store_sv(COPHH *cophh, SV *key, U32 hash,
                                    SV *value, U32 flags)

       "cop_hints_2hv"
           Generates and returns a standard Perl hash representing the full
           set of hint entries in the cop "cop".  "flags" is currently unused
           and must be zero.

            HV *  cop_hints_2hv(const COP *cop, U32 flags)

       "cop_hints_exists_pv"
           Like "cop_hints_exists_pvn", but takes a nul-terminated string
           instead of a string/length pair.

            bool  cop_hints_exists_pv(const COP *cop, const char *key,
                                      U32 hash, U32 flags)

       "cop_hints_exists_pvn"
           Look up the hint entry in the cop "cop" with the key specified by
           "keypv" and "keylen".  If "flags" has the "COPHH_KEY_UTF8" bit set,
           the key octets are interpreted as UTF-8, otherwise they are
           interpreted as Latin-1.  "hash" is a precomputed hash of the key
           string, or zero if it has not been precomputed.  Returns true if a
           value exists, and false otherwise.

            bool  cop_hints_exists_pvn(const COP *cop, const char *keypv,
                                       STRLEN keylen, U32 hash, U32 flags)

       "cop_hints_exists_pvs"
           Like "cop_hints_exists_pvn", but takes a literal string instead of
           a string/length pair, and no precomputed hash.

            bool  cop_hints_exists_pvs(const COP *cop, "key", U32 flags)

       "cop_hints_exists_sv"
           Like "cop_hints_exists_pvn", but takes a Perl scalar instead of a
           string/length pair.

            bool  cop_hints_exists_sv(const COP *cop, SV *key, U32 hash,
                                      U32 flags)

       "cop_hints_fetch_pv"
           Like "cop_hints_fetch_pvn", but takes a nul-terminated string
           instead of a string/length pair.

            SV *  cop_hints_fetch_pv(const COP *cop, const char *key,
                                     U32 hash, U32 flags)

       "cop_hints_fetch_pvn"
           Look up the hint entry in the cop "cop" with the key specified by
           "keypv" and "keylen".  If "flags" has the "COPHH_KEY_UTF8" bit set,
           the key octets are interpreted as UTF-8, otherwise they are
           interpreted as Latin-1.  "hash" is a precomputed hash of the key
           string, or zero if it has not been precomputed.  Returns a mortal
           scalar copy of the value associated with the key, or
           &PL_sv_placeholder if there is no value associated with the key.

            SV *  cop_hints_fetch_pvn(const COP *cop, const char *keypv,
                                      STRLEN keylen, U32 hash, U32 flags)

       "cop_hints_fetch_pvs"
           Like "cop_hints_fetch_pvn", but takes a literal string instead of a
           string/length pair, and no precomputed hash.

            SV *  cop_hints_fetch_pvs(const COP *cop, "key", U32 flags)

       "cop_hints_fetch_sv"
           Like "cop_hints_fetch_pvn", but takes a Perl scalar instead of a
           string/length pair.

            SV *  cop_hints_fetch_sv(const COP *cop, SV *key, U32 hash,
                                     U32 flags)

       "CopLABEL"
           Returns the label attached to a cop.

            const char *  CopLABEL(COP *const cop)

       "CopLABEL_len"
           Returns the label attached to a cop, and stores its length in bytes
           into *len.

            const char *  CopLABEL_len(COP *const cop, STRLEN *len)

       "CopLABEL_len_flags"
           Returns the label attached to a cop, and stores its length in bytes
           into *len.  Upon return, *flags will be set to either "SVf_UTF8" or
           0.

            const char *  CopLABEL_len_flags(COP *const cop, STRLEN *len,
                                             U32 *flags)

       "CopLINE"
           Returns the line number in the source code associated with the
           "COP" "c"

            STRLEN  CopLINE(const COP * c)

       "CopSTASH"
           Returns the stash associated with "c".

            HV *  CopSTASH(const COP * c)

       "CopSTASH_eq"
           Returns a boolean as to whether or not "hv" is the stash associated
           with "c".

            bool  CopSTASH_eq(const COP * c, const HV * hv)

       "CopSTASHPV"
           Returns the package name of the stash associated with "c", or
           "NULL" if no associated stash

            char *  CopSTASHPV(const COP * c)

       "CopSTASHPV_set"
           Set the package name of the stash associated with "c", to the NUL-
           terminated C string "p", creating the package if necessary.

            void  CopSTASHPV_set(COP * c, const char * pv)

       "CopSTASH_set"
           Set the stash associated with "c" to "hv".

            bool  CopSTASH_set(COP * c, HV * hv)

       "cop_store_label"
           NOTE: "cop_store_label" is experimental and may change or be
           removed without notice.

           Save a label into a "cop_hints_hash".  You need to set flags to
           "SVf_UTF8" for a UTF-8 label.  Any other flag is ignored.

            void  cop_store_label(COP *const cop, const char *label,
                                  STRLEN len, U32 flags)

       "PERL_SI"
           Use this typedef to declare variables that are to hold "struct
           stackinfo".


Custom Operators

       "custom_op_desc"
           "DEPRECATED!"  It is planned to remove "custom_op_desc" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           Return the description of a given custom op.  This was once used by
           the "OP_DESC" macro, but is no longer: it has only been kept for
           compatibility, and should not be used.

            const char *  custom_op_desc(const OP *o)

       "custom_op_name"
           "DEPRECATED!"  It is planned to remove "custom_op_name" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           Return the name for a given custom op.  This was once used by the
           "OP_NAME" macro, but is no longer: it has only been kept for
           compatibility, and should not be used.

            const char *  custom_op_name(const OP *o)

       "custom_op_register"
           Register a custom op.  See "Custom Operators" in perlguts.

           NOTE: "custom_op_register" must be explicitly called as
           "Perl_custom_op_register" with an "aTHX_" parameter.

            void  Perl_custom_op_register(pTHX_ Perl_ppaddr_t ppaddr,
                                          const XOP *xop)

       "Perl_custom_op_xop"
           Return the XOP structure for a given custom op.  This macro should
           be considered internal to "OP_NAME" and the other access macros:
           use them instead.  This macro does call a function.  Prior to
           5.19.6, this was implemented as a function.

            const XOP *  Perl_custom_op_xop(pTHX_ const OP *o)

       "XopDISABLE"
           Temporarily disable a member of the XOP, by clearing the
           appropriate flag.

            void  XopDISABLE(XOP *xop, which)

       "XopENABLE"
           Reenable a member of the XOP which has been disabled.

            void  XopENABLE(XOP *xop, which)

       "XopENTRY"
           Return a member of the XOP structure.  "which" is a cpp token
           indicating which entry to return.  If the member is not set this
           will return a default value.  The return type depends on "which".
           This macro evaluates its arguments more than once.  If you are
           using "Perl_custom_op_xop" to retrieve a "XOP *" from a "OP *", use
           the more efficient "XopENTRYCUSTOM" instead.

              XopENTRY(XOP *xop, which)

       "XopENTRYCUSTOM"
           Exactly like "XopENTRY(XopENTRY(Perl_custom_op_xop(aTHX_ o),
           which)" but more efficient.  The "which" parameter is identical to
           "XopENTRY".

              XopENTRYCUSTOM(const OP *o, which)

       "XopENTRY_set"
           Set a member of the XOP structure.  "which" is a cpp token
           indicating which entry to set.  See "Custom Operators" in perlguts
           for details about the available members and how they are used.
           This macro evaluates its argument more than once.

            void  XopENTRY_set(XOP *xop, which, value)

       "XopFLAGS"
           Return the XOP's flags.

            U32  XopFLAGS(XOP *xop)


CV Handling

       This section documents functions to manipulate CVs which are code-
       values, meaning subroutines.  For more information, see perlguts.

       "caller_cx"
           The XSUB-writer's equivalent of caller().  The returned
           "PERL_CONTEXT" structure can be interrogated to find all the
           information returned to Perl by "caller".  Note that XSUBs don't
           get a stack frame, so "caller_cx(0, NULL)" will return information
           for the immediately-surrounding Perl code.

           This function skips over the automatic calls to &DB::sub made on
           the behalf of the debugger.  If the stack frame requested was a sub
           called by "DB::sub", the return value will be the frame for the
           call to "DB::sub", since that has the correct line number/etc. for
           the call site.  If dbcxp is non-"NULL", it will be set to a pointer
           to the frame for the sub call itself.

            const PERL_CONTEXT *  caller_cx(I32 level,
                                            const PERL_CONTEXT **dbcxp)

       "CvGV"
           Returns the GV associated with the CV "sv", reifying it if
           necessary.

            GV *  CvGV(CV *sv)

       "CvSTASH"
           Returns the stash of the CV.  A stash is the symbol table hash,
           containing the package-scoped variables in the package where the
           subroutine was defined.  For more information, see perlguts.

           This also has a special use with XS AUTOLOAD subs.  See
           "Autoloading with XSUBs" in perlguts.

            HV*  CvSTASH(CV* cv)

       "find_runcv"
           Locate the CV corresponding to the currently executing sub or eval.
           If "db_seqp" is non_null, skip CVs that are in the DB package and
           populate *db_seqp with the cop sequence number at the point that
           the DB:: code was entered.  (This allows debuggers to eval in the
           scope of the breakpoint rather than in the scope of the debugger
           itself.)

            CV*  find_runcv(U32 *db_seqp)

       "get_cv"
       "get_cvs"
       "get_cvn_flags"
           These return the CV of the specified Perl subroutine.  "flags" are
           passed to "gv_fetchpvn_flags".  If "GV_ADD" is set and the Perl
           subroutine does not exist then it will be declared (which has the
           same effect as saying "sub name;").  If "GV_ADD" is not set and the
           subroutine does not exist, then NULL is returned.

           The forms differ only in how the subroutine is specified..  With
           "get_cvs", the name is a literal C string, enclosed in double
           quotes.  With "get_cv", the name is given by the "name" parameter,
           which must be a NUL-terminated C string.  With "get_cvn_flags", the
           name is also given by the "name" parameter, but it is a Perl string
           (possibly containing embedded NUL bytes), and its length in bytes
           is contained in the "len" parameter.

           NOTE: the "perl_get_cv()" form is deprecated.

           NOTE: the "perl_get_cvs()" form is deprecated.

           NOTE: the "perl_get_cvn_flags()" form is deprecated.

            CV*   get_cv       (const char* name, I32 flags)
            CV *  get_cvs      ("string", I32 flags)
            CV*   get_cvn_flags(const char* name, STRLEN len, I32 flags)

       "Nullcv"
           "DEPRECATED!"  It is planned to remove "Nullcv" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Null CV pointer.

           (deprecated - use "(CV *)NULL" instead)


Debugging

       "dump_all"
           Dumps the entire optree of the current program starting at
           "PL_main_root" to "STDERR".  Also dumps the optrees for all visible
           subroutines in "PL_defstash".

            void  dump_all()

       "dump_c_backtrace"
           Dumps the C backtrace to the given "fp".

           Returns true if a backtrace could be retrieved, false if not.

            bool  dump_c_backtrace(PerlIO* fp, int max_depth, int skip)

       "dump_packsubs"
           Dumps the optrees for all visible subroutines in "stash".

            void  dump_packsubs(const HV* stash)

       "get_c_backtrace_dump"
           Returns a SV containing a dump of "depth" frames of the call stack,
           skipping the "skip" innermost ones.  "depth" of 20 is usually
           enough.

           The appended output looks like:

            ...
            1   10e004812:0082   Perl_croak   util.c:1716    /usr/bin/perl
            2   10df8d6d2:1d72   perl_parse   perl.c:3975    /usr/bin/perl
            ...

           The fields are tab-separated.  The first column is the depth (zero
           being the innermost non-skipped frame).  In the hex:offset, the hex
           is where the program counter was in "S_parse_body", and the :offset
           (might be missing) tells how much inside the "S_parse_body" the
           program counter was.

           The "util.c:1716" is the source code file and line number.

           The /usr/bin/perl is obvious (hopefully).

           Unknowns are "-".  Unknowns can happen unfortunately quite easily:
           if the platform doesn't support retrieving the information; if the
           binary is missing the debug information; if the optimizer has
           transformed the code by for example inlining.

            SV*  get_c_backtrace_dump(int max_depth, int skip)

       "HAS_BACKTRACE"
           This symbol, if defined, indicates that the "backtrace()" routine
           is available to get a stack trace.  The execinfo.h header must be
           included to use this routine.

       "op_class"
           Given an op, determine what type of struct it has been allocated
           as.  Returns one of the OPclass enums, such as OPclass_LISTOP.

            OPclass  op_class(const OP *o)

       "op_dump"
           Dumps the optree starting at OP "o" to "STDERR".

            void  op_dump(const OP *o)

       "sv_dump"
           Dumps the contents of an SV to the "STDERR" filehandle.

           For an example of its output, see Devel::Peek.

            void  sv_dump(SV* sv)


Display functions

       "form"
       "form_nocontext"
           These take a sprintf-style format pattern and conventional (non-SV)
           arguments and return the formatted string.

               (char *) Perl_form(pTHX_ const char* pat, ...)

           can be used any place a string (char *) is required:

               char * s = Perl_form("%d.%d",major,minor);

           They use a single (per-thread) private buffer so if you want to
           format several strings you must explicitly copy the earlier strings
           away (and free the copies when you are done).

           The two forms differ only in that "form_nocontext" does not take a
           thread context ("aTHX") parameter, so is used in situations where
           the caller doesn't already have the thread context.

           NOTE: "form" must be explicitly called as "Perl_form" with an
           "aTHX_" parameter.

            char*  Perl_form     (pTHX_ const char* pat, ...)
            char*  form_nocontext(const char* pat, ...)

       "mess"
       "mess_nocontext"
           These take a sprintf-style format pattern and argument list, which
           are used to generate a string message.  If the message does not end
           with a newline, then it will be extended with some indication of
           the current location in the code, as described for "mess_sv".

           Normally, the resulting message is returned in a new mortal SV.
           But during global destruction a single SV may be shared between
           uses of this function.

           The two forms differ only in that "mess_nocontext" does not take a
           thread context ("aTHX") parameter, so is used in situations where
           the caller doesn't already have the thread context.

           NOTE: "mess" must be explicitly called as "Perl_mess" with an
           "aTHX_" parameter.

            SV*  Perl_mess     (pTHX_ const char* pat, ...)
            SV*  mess_nocontext(const char* pat, ...)

       "mess_sv"
           Expands a message, intended for the user, to include an indication
           of the current location in the code, if the message does not
           already appear to be complete.

           "basemsg" is the initial message or object.  If it is a reference,
           it will be used as-is and will be the result of this function.
           Otherwise it is used as a string, and if it already ends with a
           newline, it is taken to be complete, and the result of this
           function will be the same string.  If the message does not end with
           a newline, then a segment such as "at foo.pl line 37" will be
           appended, and possibly other clauses indicating the current state
           of execution.  The resulting message will end with a dot and a
           newline.

           Normally, the resulting message is returned in a new mortal SV.
           During global destruction a single SV may be shared between uses of
           this function.  If "consume" is true, then the function is
           permitted (but not required) to modify and return "basemsg" instead
           of allocating a new SV.

            SV*  mess_sv(SV* basemsg, bool consume)

       "pv_display"
           Similar to

             pv_escape(dsv,pv,cur,pvlim,PERL_PV_ESCAPE_QUOTE);

           except that an additional "\0" will be appended to the string when
           len > cur and pv[cur] is "\0".

           Note that the final string may be up to 7 chars longer than pvlim.

            char*  pv_display(SV *dsv, const char *pv, STRLEN cur, STRLEN len,
                              STRLEN pvlim)

       "pv_escape"
           Escapes at most the first "count" chars of "pv" and puts the
           results into "dsv" such that the size of the escaped string will
           not exceed "max" chars and will not contain any incomplete escape
           sequences.  The number of bytes escaped will be returned in the
           "STRLEN *escaped" parameter if it is not null.  When the "dsv"
           parameter is null no escaping actually occurs, but the number of
           bytes that would be escaped were it not null will be calculated.

           If flags contains "PERL_PV_ESCAPE_QUOTE" then any double quotes in
           the string will also be escaped.

           Normally the SV will be cleared before the escaped string is
           prepared, but when "PERL_PV_ESCAPE_NOCLEAR" is set this will not
           occur.

           If "PERL_PV_ESCAPE_UNI" is set then the input string is treated as
           UTF-8 if "PERL_PV_ESCAPE_UNI_DETECT" is set then the input string
           is scanned using "is_utf8_string()" to determine if it is UTF-8.

           If "PERL_PV_ESCAPE_ALL" is set then all input chars will be output
           using "\x01F1" style escapes, otherwise if
           "PERL_PV_ESCAPE_NONASCII" is set, only non-ASCII chars will be
           escaped using this style; otherwise, only chars above 255 will be
           so escaped; other non printable chars will use octal or common
           escaped patterns like "\n".  Otherwise, if
           "PERL_PV_ESCAPE_NOBACKSLASH" then all chars below 255 will be
           treated as printable and will be output as literals.

           If "PERL_PV_ESCAPE_FIRSTCHAR" is set then only the first char of
           the string will be escaped, regardless of max.  If the output is to
           be in hex, then it will be returned as a plain hex sequence.  Thus
           the output will either be a single char, an octal escape sequence,
           a special escape like "\n" or a hex value.

           If "PERL_PV_ESCAPE_RE" is set then the escape char used will be a
           "%" and not a "\\".  This is because regexes very often contain
           backslashed sequences, whereas "%" is not a particularly common
           character in patterns.

           Returns a pointer to the escaped text as held by "dsv".

            char*  pv_escape(SV *dsv, char const * const str,
                             const STRLEN count, const STRLEN max,
                             STRLEN * const escaped, const U32 flags)

       "pv_pretty"
           Converts a string into something presentable, handling escaping via
           "pv_escape()" and supporting quoting and ellipses.

           If the "PERL_PV_PRETTY_QUOTE" flag is set then the result will be
           double quoted with any double quotes in the string escaped.
           Otherwise if the "PERL_PV_PRETTY_LTGT" flag is set then the result
           be wrapped in angle brackets.

           If the "PERL_PV_PRETTY_ELLIPSES" flag is set and not all characters
           in string were output then an ellipsis "..." will be appended to
           the string.  Note that this happens AFTER it has been quoted.

           If "start_color" is non-null then it will be inserted after the
           opening quote (if there is one) but before the escaped text.  If
           "end_color" is non-null then it will be inserted after the escaped
           text but before any quotes or ellipses.

           Returns a pointer to the prettified text as held by "dsv".

            char*  pv_pretty(SV *dsv, char const * const str,
                             const STRLEN count, const STRLEN max,
                             char const * const start_color,
                             char const * const end_color, const U32 flags)

       "vform"
           Like "form" but but the arguments are an encapsulated argument
           list.

            char*  vform(const char* pat, va_list* args)

       "vmess"
           "pat" and "args" are a sprintf-style format pattern and
           encapsulated argument list, respectively.  These are used to
           generate a string message.  If the message does not end with a
           newline, then it will be extended with some indication of the
           current location in the code, as described for "mess_sv".

           Normally, the resulting message is returned in a new mortal SV.
           During global destruction a single SV may be shared between uses of
           this function.

            SV*  vmess(const char* pat, va_list* args)


Embedding and Interpreter Cloning

       "cv_clone"
           Clone a CV, making a lexical closure.  "proto" supplies the
           prototype of the function: its code, pad structure, and other
           attributes.  The prototype is combined with a capture of outer
           lexicals to which the code refers, which are taken from the
           currently-executing instance of the immediately surrounding code.

            CV*  cv_clone(CV* proto)

       "cv_name"
           Returns an SV containing the name of the CV, mainly for use in
           error reporting.  The CV may actually be a GV instead, in which
           case the returned SV holds the GV's name.  Anything other than a GV
           or CV is treated as a string already holding the sub name, but this
           could change in the future.

           An SV may be passed as a second argument.  If so, the name will be
           assigned to it and it will be returned.  Otherwise the returned SV
           will be a new mortal.

           If "flags" has the "CV_NAME_NOTQUAL" bit set, then the package name
           will not be included.  If the first argument is neither a CV nor a
           GV, this flag is ignored (subject to change).

            SV *  cv_name(CV *cv, SV *sv, U32 flags)

       "cv_undef"
           Clear out all the active components of a CV.  This can happen
           either by an explicit "undef &foo", or by the reference count going
           to zero.  In the former case, we keep the "CvOUTSIDE" pointer, so
           that any anonymous children can still follow the full lexical scope
           chain.

            void  cv_undef(CV* cv)

       "find_rundefsv"
           Returns the global variable $_.

            SV*  find_rundefsv()

       "find_rundefsvoffset"
           "DEPRECATED!"  It is planned to remove "find_rundefsvoffset" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           Until the lexical $_ feature was removed, this function would find
           the position of the lexical $_ in the pad of the currently-
           executing function and return the offset in the current pad, or
           "NOT_IN_PAD".

           Now it always returns "NOT_IN_PAD".

            PADOFFSET  find_rundefsvoffset()

       "intro_my"
           "Introduce" "my" variables to visible status.  This is called
           during parsing at the end of each statement to make lexical
           variables visible to subsequent statements.

            U32  intro_my()

       "load_module"
           Loads the module whose name is pointed to by the string part of
           "name".  Note that the actual module name, not its filename, should
           be given.  Eg, "Foo::Bar" instead of "Foo/Bar.pm". ver, if
           specified and not NULL, provides version semantics similar to "use
           Foo::Bar VERSION". The optional trailing arguments can be used to
           specify arguments to the module's "import()" method, similar to
           "use Foo::Bar VERSION LIST"; their precise handling depends on the
           flags. The flags argument is a bitwise-ORed collection of any of
           "PERL_LOADMOD_DENY", "PERL_LOADMOD_NOIMPORT", or
           "PERL_LOADMOD_IMPORT_OPS" (or 0 for no flags).

           If "PERL_LOADMOD_NOIMPORT" is set, the module is loaded as if with
           an empty import list, as in "use Foo::Bar ()"; this is the only
           circumstance in which the trailing optional arguments may be
           omitted entirely. Otherwise, if "PERL_LOADMOD_IMPORT_OPS" is set,
           the trailing arguments must consist of exactly one "OP*",
           containing the op tree that produces the relevant import arguments.
           Otherwise, the trailing arguments must all be "SV*" values that
           will be used as import arguments; and the list must be terminated
           with "(SV*) NULL". If neither "PERL_LOADMOD_NOIMPORT" nor
           "PERL_LOADMOD_IMPORT_OPS" is set, the trailing "NULL" pointer is
           needed even if no import arguments are desired. The reference count
           for each specified "SV*" argument is decremented. In addition, the
           "name" argument is modified.

           If "PERL_LOADMOD_DENY" is set, the module is loaded as if with "no"
           rather than "use".

            void  load_module(U32 flags, SV* name, SV* ver, ...)

       "load_module_nocontext"
           Like "load_module" but does not take a thread context ("aTHX")
           parameter, so is used in situations where the caller doesn't
           already have the thread context.

            void  load_module_nocontext(U32 flags, SV* name, SV* ver, ...)

       "my_exit"
           A wrapper for the C library exit(3), honoring what "PL_exit_flags"
           in perlapi say to do.

            void  my_exit(U32 status)

       "newPADNAMELIST"
           NOTE: "newPADNAMELIST" is experimental and may change or be removed
           without notice.

           Creates a new pad name list.  "max" is the highest index for which
           space is allocated.

            PADNAMELIST *  newPADNAMELIST(size_t max)

       "newPADNAMEouter"
           NOTE: "newPADNAMEouter" is experimental and may change or be
           removed without notice.

           Constructs and returns a new pad name.  Only use this function for
           names that refer to outer lexicals.  (See also "newPADNAMEpvn".)
           "outer" is the outer pad name that this one mirrors.  The returned
           pad name has the "PADNAMEt_OUTER" flag already set.

            PADNAME *  newPADNAMEouter(PADNAME *outer)

       "newPADNAMEpvn"
           NOTE: "newPADNAMEpvn" is experimental and may change or be removed
           without notice.

           Constructs and returns a new pad name.  "s" must be a UTF-8 string.
           Do not use this for pad names that point to outer lexicals.  See
           "newPADNAMEouter".

            PADNAME *  newPADNAMEpvn(const char *s, STRLEN len)

       "nothreadhook"
           Stub that provides thread hook for perl_destruct when there are no
           threads.

            int  nothreadhook()

       "pad_add_anon"
           Allocates a place in the currently-compiling pad (via "pad_alloc")
           for an anonymous function that is lexically scoped inside the
           currently-compiling function.  The function "func" is linked into
           the pad, and its "CvOUTSIDE" link to the outer scope is weakened to
           avoid a reference loop.

           One reference count is stolen, so you may need to do
           "SvREFCNT_inc(func)".

           "optype" should be an opcode indicating the type of operation that
           the pad entry is to support.  This doesn't affect operational
           semantics, but is used for debugging.

            PADOFFSET  pad_add_anon(CV* func, I32 optype)

       "pad_add_name_pv"
           Exactly like "pad_add_name_pvn", but takes a nul-terminated string
           instead of a string/length pair.

            PADOFFSET  pad_add_name_pv(const char *name, const U32 flags,
                                       HV *typestash, HV *ourstash)

       "pad_add_name_pvn"
           Allocates a place in the currently-compiling pad for a named
           lexical variable.  Stores the name and other metadata in the name
           part of the pad, and makes preparations to manage the variable's
           lexical scoping.  Returns the offset of the allocated pad slot.

           "namepv"/"namelen" specify the variable's name, including leading
           sigil.  If "typestash" is non-null, the name is for a typed
           lexical, and this identifies the type.  If "ourstash" is non-null,
           it's a lexical reference to a package variable, and this identifies
           the package.  The following flags can be OR'ed together:

            padadd_OUR          redundantly specifies if it's a package var
            padadd_STATE        variable will retain value persistently
            padadd_NO_DUP_CHECK skip check for lexical shadowing

            PADOFFSET  pad_add_name_pvn(const char *namepv, STRLEN namelen,
                                        U32 flags, HV *typestash,
                                        HV *ourstash)

       "pad_add_name_sv"
           Exactly like "pad_add_name_pvn", but takes the name string in the
           form of an SV instead of a string/length pair.

            PADOFFSET  pad_add_name_sv(SV *name, U32 flags, HV *typestash,
                                       HV *ourstash)

       "pad_alloc"
           NOTE: "pad_alloc" is experimental and may change or be removed
           without notice.

           Allocates a place in the currently-compiling pad, returning the
           offset of the allocated pad slot.  No name is initially attached to
           the pad slot.  "tmptype" is a set of flags indicating the kind of
           pad entry required, which will be set in the value SV for the
           allocated pad entry:

               SVs_PADMY    named lexical variable ("my", "our", "state")
               SVs_PADTMP   unnamed temporary store
               SVf_READONLY constant shared between recursion levels

           "SVf_READONLY" has been supported here only since perl 5.20.  To
           work with earlier versions as well, use "SVf_READONLY|SVs_PADTMP".
           "SVf_READONLY" does not cause the SV in the pad slot to be marked
           read-only, but simply tells "pad_alloc" that it will be made read-
           only (by the caller), or at least should be treated as such.

           "optype" should be an opcode indicating the type of operation that
           the pad entry is to support.  This doesn't affect operational
           semantics, but is used for debugging.

            PADOFFSET  pad_alloc(I32 optype, U32 tmptype)

       "pad_findmy_pv"
           Exactly like "pad_findmy_pvn", but takes a nul-terminated string
           instead of a string/length pair.

            PADOFFSET  pad_findmy_pv(const char* name, U32 flags)

       "pad_findmy_pvn"
           Given the name of a lexical variable, find its position in the
           currently-compiling pad.  "namepv"/"namelen" specify the variable's
           name, including leading sigil.  "flags" is reserved and must be
           zero.  If it is not in the current pad but appears in the pad of
           any lexically enclosing scope, then a pseudo-entry for it is added
           in the current pad.  Returns the offset in the current pad, or
           "NOT_IN_PAD" if no such lexical is in scope.

            PADOFFSET  pad_findmy_pvn(const char* namepv, STRLEN namelen,
                                      U32 flags)

       "pad_findmy_sv"
           Exactly like "pad_findmy_pvn", but takes the name string in the
           form of an SV instead of a string/length pair.

            PADOFFSET  pad_findmy_sv(SV* name, U32 flags)

       "padnamelist_fetch"
           NOTE: "padnamelist_fetch" is experimental and may change or be
           removed without notice.

           Fetches the pad name from the given index.

            PADNAME *  padnamelist_fetch(PADNAMELIST *pnl, SSize_t key)

       "padnamelist_store"
           NOTE: "padnamelist_store" is experimental and may change or be
           removed without notice.

           Stores the pad name (which may be null) at the given index, freeing
           any existing pad name in that slot.

            PADNAME **  padnamelist_store(PADNAMELIST *pnl, SSize_t key,
                                          PADNAME *val)

       "pad_tidy"
           NOTE: "pad_tidy" is experimental and may change or be removed
           without notice.

           Tidy up a pad at the end of compilation of the code to which it
           belongs.  Jobs performed here are: remove most stuff from the pads
           of anonsub prototypes; give it a @_; mark temporaries as such.
           "type" indicates the kind of subroutine:

               padtidy_SUB        ordinary subroutine
               padtidy_SUBCLONE   prototype for lexical closure
               padtidy_FORMAT     format

            void  pad_tidy(padtidy_type type)

       "perl_alloc"
           Allocates a new Perl interpreter.  See perlembed.

            PerlInterpreter*  perl_alloc()

       "PERL_ASYNC_CHECK"
           Described in perlinterp.

            void  PERL_ASYNC_CHECK()

       "perl_clone"
           Create and return a new interpreter by cloning the current one.

           "perl_clone" takes these flags as parameters:

           "CLONEf_COPY_STACKS" - is used to, well, copy the stacks also,
           without it we only clone the data and zero the stacks, with it we
           copy the stacks and the new perl interpreter is ready to run at the
           exact same point as the previous one.  The pseudo-fork code uses
           "COPY_STACKS" while the threads->create doesn't.

           "CLONEf_KEEP_PTR_TABLE" - "perl_clone" keeps a ptr_table with the
           pointer of the old variable as a key and the new variable as a
           value, this allows it to check if something has been cloned and not
           clone it again, but rather just use the value and increase the
           refcount.  If "KEEP_PTR_TABLE" is not set then "perl_clone" will
           kill the ptr_table using the function
           "ptr_table_free(PL_ptr_table); PL_ptr_table = NULL;".  A reason to
           keep it around is if you want to dup some of your own variables
           which are outside the graph that perl scans.

           "CLONEf_CLONE_HOST" - This is a win32 thing, it is ignored on unix,
           it tells perl's win32host code (which is c++) to clone itself, this
           is needed on win32 if you want to run two threads at the same time,
           if you just want to do some stuff in a separate perl interpreter
           and then throw it away and return to the original one, you don't
           need to do anything.

            PerlInterpreter*  perl_clone(PerlInterpreter *proto_perl,
                                         UV flags)

       "perl_construct"
           Initializes a new Perl interpreter.  See perlembed.

            void  perl_construct(PerlInterpreter *my_perl)

       "perl_destruct"
           Shuts down a Perl interpreter.  See perlembed for a tutorial.

           "my_perl" points to the Perl interpreter.  It must have been
           previously created through the use of "perl_alloc" and
           "perl_construct".  It may have been initialised through
           "perl_parse", and may have been used through "perl_run" and other
           means.  This function should be called for any Perl interpreter
           that has been constructed with "perl_construct", even if subsequent
           operations on it failed, for example if "perl_parse" returned a
           non-zero value.

           If the interpreter's "PL_exit_flags" word has the
           "PERL_EXIT_DESTRUCT_END" flag set, then this function will execute
           code in "END" blocks before performing the rest of destruction.  If
           it is desired to make any use of the interpreter between
           "perl_parse" and "perl_destruct" other than just calling
           "perl_run", then this flag should be set early on.  This matters if
           "perl_run" will not be called, or if anything else will be done in
           addition to calling "perl_run".

           Returns a value be a suitable value to pass to the C library
           function "exit" (or to return from "main"), to serve as an exit
           code indicating the nature of the way the interpreter terminated.
           This takes into account any failure of "perl_parse" and any early
           exit from "perl_run".  The exit code is of the type required by the
           host operating system, so because of differing exit code
           conventions it is not portable to interpret specific numeric values
           as having specific meanings.

            int  perl_destruct(PerlInterpreter *my_perl)

       "perl_free"
           Releases a Perl interpreter.  See perlembed.

            void  perl_free(PerlInterpreter *my_perl)

       "perl_parse"
           Tells a Perl interpreter to parse a Perl script.  This performs
           most of the initialisation of a Perl interpreter.  See perlembed
           for a tutorial.

           "my_perl" points to the Perl interpreter that is to parse the
           script.  It must have been previously created through the use of
           "perl_alloc" and "perl_construct".  "xsinit" points to a callback
           function that will be called to set up the ability for this Perl
           interpreter to load XS extensions, or may be null to perform no
           such setup.

           "argc" and "argv" supply a set of command-line arguments to the
           Perl interpreter, as would normally be passed to the "main"
           function of a C program.  "argv[argc]" must be null.  These
           arguments are where the script to parse is specified, either by
           naming a script file or by providing a script in a "-e" option.  If
           $0 will be written to in the Perl interpreter, then the argument
           strings must be in writable memory, and so mustn't just be string
           constants.

           "env" specifies a set of environment variables that will be used by
           this Perl interpreter.  If non-null, it must point to a null-
           terminated array of environment strings.  If null, the Perl
           interpreter will use the environment supplied by the "environ"
           global variable.

           This function initialises the interpreter, and parses and compiles
           the script specified by the command-line arguments.  This includes
           executing code in "BEGIN", "UNITCHECK", and "CHECK" blocks.  It
           does not execute "INIT" blocks or the main program.

           Returns an integer of slightly tricky interpretation.  The correct
           use of the return value is as a truth value indicating whether
           there was a failure in initialisation.  If zero is returned, this
           indicates that initialisation was successful, and it is safe to
           proceed to call "perl_run" and make other use of it.  If a non-zero
           value is returned, this indicates some problem that means the
           interpreter wants to terminate.  The interpreter should not be just
           abandoned upon such failure; the caller should proceed to shut the
           interpreter down cleanly with "perl_destruct" and free it with
           "perl_free".

           For historical reasons, the non-zero return value also attempts to
           be a suitable value to pass to the C library function "exit" (or to
           return from "main"), to serve as an exit code indicating the nature
           of the way initialisation terminated.  However, this isn't
           portable, due to differing exit code conventions.  A historical bug
           is preserved for the time being: if the Perl built-in "exit" is
           called during this function's execution, with a type of exit
           entailing a zero exit code under the host operating system's
           conventions, then this function returns zero rather than a non-zero
           value.  This bug, [perl #2754], leads to "perl_run" being called
           (and therefore "INIT" blocks and the main program running) despite
           a call to "exit".  It has been preserved because a popular module-
           installing module has come to rely on it and needs time to be
           fixed.  This issue is [perl #132577], and the original bug is due
           to be fixed in Perl 5.30.

            int  perl_parse(PerlInterpreter *my_perl, XSINIT_t xsinit,
                            int argc, char** argv, char** env)

       "perl_run"
           Tells a Perl interpreter to run its main program.  See perlembed
           for a tutorial.

           "my_perl" points to the Perl interpreter.  It must have been
           previously created through the use of "perl_alloc" and
           "perl_construct", and initialised through "perl_parse".  This
           function should not be called if "perl_parse" returned a non-zero
           value, indicating a failure in initialisation or compilation.

           This function executes code in "INIT" blocks, and then executes the
           main program.  The code to be executed is that established by the
           prior call to "perl_parse".  If the interpreter's "PL_exit_flags"
           word does not have the "PERL_EXIT_DESTRUCT_END" flag set, then this
           function will also execute code in "END" blocks.  If it is desired
           to make any further use of the interpreter after calling this
           function, then "END" blocks should be postponed to "perl_destruct"
           time by setting that flag.

           Returns an integer of slightly tricky interpretation.  The correct
           use of the return value is as a truth value indicating whether the
           program terminated non-locally.  If zero is returned, this
           indicates that the program ran to completion, and it is safe to
           make other use of the interpreter (provided that the
           "PERL_EXIT_DESTRUCT_END" flag was set as described above).  If a
           non-zero value is returned, this indicates that the interpreter
           wants to terminate early.  The interpreter should not be just
           abandoned because of this desire to terminate; the caller should
           proceed to shut the interpreter down cleanly with "perl_destruct"
           and free it with "perl_free".

           For historical reasons, the non-zero return value also attempts to
           be a suitable value to pass to the C library function "exit" (or to
           return from "main"), to serve as an exit code indicating the nature
           of the way the program terminated.  However, this isn't portable,
           due to differing exit code conventions.  An attempt is made to
           return an exit code of the type required by the host operating
           system, but because it is constrained to be non-zero, it is not
           necessarily possible to indicate every type of exit.  It is only
           reliable on Unix, where a zero exit code can be augmented with a
           set bit that will be ignored.  In any case, this function is not
           the correct place to acquire an exit code: one should get that from
           "perl_destruct".

            int  perl_run(PerlInterpreter *my_perl)

       "PERL_SYS_INIT"
           Provides system-specific tune up of the C runtime environment
           necessary to run Perl interpreters.  This should be called only
           once, before creating any Perl interpreters.

            void  PERL_SYS_INIT(int *argc, char*** argv)

       "PERL_SYS_INIT3"
           Provides system-specific tune up of the C runtime environment
           necessary to run Perl interpreters.  This should be called only
           once, before creating any Perl interpreters.

            void  PERL_SYS_INIT3(int *argc, char*** argv, char*** env)

       "PERL_SYS_TERM"
           Provides system-specific clean up of the C runtime environment
           after running Perl interpreters.  This should be called only once,
           after freeing any remaining Perl interpreters.

            void  PERL_SYS_TERM()

       "PL_exit_flags"
           Contains flags controlling perl's behaviour on exit():

           o   "PERL_EXIT_DESTRUCT_END"

               If set, END blocks are executed when the interpreter is
               destroyed.  This is normally set by perl itself after the
               interpreter is constructed.

           o   "PERL_EXIT_ABORT"

               Call "abort()" on exit.  This is used internally by perl itself
               to abort if exit is called while processing exit.

           o   "PERL_EXIT_WARN"

               Warn on exit.

           o   "PERL_EXIT_EXPECTED"

               Set by the "exit" in perlfunc operator.

            U8  PL_exit_flags

       "PL_perl_destruct_level"
           This value may be set when embedding for full cleanup.

           Possible values:

           o   0 - none

           o   1 - full

           o   2 or greater - full with checks.

           If $ENV{PERL_DESTRUCT_LEVEL} is set to an integer greater than the
           value of "PL_perl_destruct_level" its value is used instead.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            signed char  PL_perl_destruct_level

       "require_pv"
           Tells Perl to "require" the file named by the string argument.  It
           is analogous to the Perl code "eval "require '$file'"".  It's even
           implemented that way; consider using load_module instead.

           NOTE: the "perl_require_pv()" form is deprecated.

            void  require_pv(const char* pv)

       "UVf"
           "DEPRECATED!"  It is planned to remove "UVf" from a future release
           of Perl.  Do not use it for new code; remove it from existing code.

           Obsolete form of "UVuf", which you should convert to instead use

            const char *  UVf

       "vload_module"
           Like "load_module" but the arguments are an encapsulated argument
           list.

            void  vload_module(U32 flags, SV* name, SV* ver, va_list* args)


Errno

       "sv_string_from_errnum"
           Generates the message string describing an OS error and returns it
           as an SV.  "errnum" must be a value that "errno" could take,
           identifying the type of error.

           If "tgtsv" is non-null then the string will be written into that SV
           (overwriting existing content) and it will be returned.  If "tgtsv"
           is a null pointer then the string will be written into a new mortal
           SV which will be returned.

           The message will be taken from whatever locale would be used by $!,
           and will be encoded in the SV in whatever manner would be used by
           $!.  The details of this process are subject to future change.
           Currently, the message is taken from the C locale by default
           (usually producing an English message), and from the currently
           selected locale when in the scope of the "use locale" pragma.  A
           heuristic attempt is made to decode the message from the locale's
           character encoding, but it will only be decoded as either UTF-8 or
           ISO-8859-1.  It is always correctly decoded in a UTF-8 locale,
           usually in an ISO-8859-1 locale, and never in any other locale.

           The SV is always returned containing an actual string, and with no
           other OK bits set.  Unlike $!, a message is even yielded for
           "errnum" zero (meaning success), and if no useful message is
           available then a useless string (currently empty) is returned.

            SV*  sv_string_from_errnum(int errnum, SV* tgtsv)


Exception Handling (simple) Macros

       "dXCPT"
           Set up necessary local variables for exception handling.  See
           "Exception Handling" in perlguts.

              dXCPT;

       "JMPENV_JUMP"
           Described in perlinterp.

            void  JMPENV_JUMP(int v)

       "JMPENV_PUSH"
           Described in perlinterp.

            void  JMPENV_PUSH(int v)

       "PL_restartop"
           Described in perlinterp.

       "XCPT_CATCH"
           Introduces a catch block.  See "Exception Handling" in perlguts.

       "XCPT_RETHROW"
           Rethrows a previously caught exception.  See "Exception Handling"
           in perlguts.

              XCPT_RETHROW;

       "XCPT_TRY_END"
           Ends a try block.  See "Exception Handling" in perlguts.

       "XCPT_TRY_START"
           Starts a try block.  See "Exception Handling" in perlguts.


Filesystem configuration values

       Also see "List of capability HAS_foo symbols".

       "DIRNAMLEN"
           This symbol, if defined, indicates to the C program that the length
           of directory entry names is provided by a "d_namlen" field.
           Otherwise you need to do "strlen()" on the "d_name" field.

       "DOSUID"
           This symbol, if defined, indicates that the C program should check
           the script that it is executing for setuid/setgid bits, and attempt
           to emulate setuid/setgid on systems that have disabled setuid #!
           scripts because the kernel can't do it securely.  It is up to the
           package designer to make sure that this emulation is done securely.
           Among other things, it should do an fstat on the script it just
           opened to make sure it really is a setuid/setgid script, it should
           make sure the arguments passed correspond exactly to the argument
           on the #! line, and it should not trust any subprocesses to which
           it must pass the filename rather than the file descriptor of the
           script to be executed.

       "EOF_NONBLOCK"
           This symbol, if defined, indicates to the C program that a "read()"
           on a non-blocking file descriptor will return 0 on "EOF", and not
           the value held in "RD_NODATA" (-1 usually, in that case!).

       "FCNTL_CAN_LOCK"
           This symbol, if defined, indicates that "fcntl()" can be used for
           file locking.  Normally on Unix systems this is defined.  It may be
           undefined on "VMS".

       "FFLUSH_ALL"
           This symbol, if defined, tells that to flush all pending stdio
           output one must loop through all the stdio file handles stored in
           an array and fflush them.  Note that if "fflushNULL" is defined,
           fflushall will not even be probed for and will be left undefined.

       "FFLUSH_NULL"
           This symbol, if defined, tells that "fflush(NULL)" correctly
           flushes all pending stdio output without side effects. In
           particular, on some platforms calling "fflush(NULL)" *still*
           corrupts "STDIN" if it is a pipe.

       "FILE_base"
           This macro is used to access the "_base" field (or equivalent) of
           the "FILE" structure pointed to by its argument. This macro will
           always be defined if "USE_STDIO_BASE" is defined.

            void *  FILE_base(FILE * f)

       "FILE_bufsiz"
           This macro is used to determine the number of bytes in the I/O
           buffer pointed to by "_base" field (or equivalent) of the "FILE"
           structure pointed to its argument. This macro will always be
           defined if "USE_STDIO_BASE" is defined.

            Size_t  FILE_bufsiz(FILE *f)

       "FILE_cnt"
           This macro is used to access the "_cnt" field (or equivalent) of
           the "FILE" structure pointed to by its argument. This macro will
           always be defined if "USE_STDIO_PTR" is defined.

            Size_t  FILE_cnt(FILE * f)

       "FILE_ptr"
           This macro is used to access the "_ptr" field (or equivalent) of
           the "FILE" structure pointed to by its argument. This macro will
           always be defined if "USE_STDIO_PTR" is defined.

            void *  FILE_ptr(FILE * f)

       "FLEXFILENAMES"
           This symbol, if defined, indicates that the system supports
           filenames longer than 14 characters.

       "HAS_DIR_DD_FD"
           This symbol, if defined, indicates that the the "DIR"* dirstream
           structure contains a member variable named "dd_fd".

       "HAS_DUP2"
           This symbol, if defined, indicates that the "dup2" routine is
           available to duplicate file descriptors.

       "HAS_DUP3"
           This symbol, if defined, indicates that the "dup3" routine is
           available to duplicate file descriptors.

       "HAS_FAST_STDIO"
           This symbol, if defined, indicates that the "fast stdio" is
           available to manipulate the stdio buffers directly.

       "HAS_FCHDIR"
           This symbol, if defined, indicates that the "fchdir" routine is
           available to change directory using a file descriptor.

       "HAS_FCNTL"
           This symbol, if defined, indicates to the C program that the
           "fcntl()" function exists.

       "HAS_FDCLOSE"
           This symbol, if defined, indicates that the "fdclose" routine is
           available to free a "FILE" structure without closing the underlying
           file descriptor.  This function appeared in "FreeBSD" 10.2.

       "HAS_FPATHCONF"
           This symbol, if defined, indicates that "pathconf()" is available
           to determine file-system related limits and options associated with
           a given open file descriptor.

       "HAS_FPOS64_T"
           This symbol will be defined if the C compiler supports "fpos64_t".

       "HAS_FSTATFS"
           This symbol, if defined, indicates that the "fstatfs" routine is
           available to stat filesystems by file descriptors.

       "HAS_FSTATVFS"
           This symbol, if defined, indicates that the "fstatvfs" routine is
           available to stat filesystems by file descriptors.

       "HAS_GETFSSTAT"
           This symbol, if defined, indicates that the "getfsstat" routine is
           available to stat filesystems in bulk.

       "HAS_GETMNT"
           This symbol, if defined, indicates that the "getmnt" routine is
           available to get filesystem mount info by filename.

       "HAS_GETMNTENT"
           This symbol, if defined, indicates that the "getmntent" routine is
           available to iterate through mounted file systems to get their
           info.

       "HAS_HASMNTOPT"
           This symbol, if defined, indicates that the "hasmntopt" routine is
           available to query the mount options of file systems.

       "HAS_LSEEK_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "lseek()" function.  Otherwise, it is up to the
           program to supply one.  A good guess is

            extern off_t lseek(int, off_t, int);

       "HAS_MKDIR"
           This symbol, if defined, indicates that the "mkdir" routine is
           available to create directories.  Otherwise you should fork off a
           new process to exec /bin/mkdir.

       "HAS_OFF64_T"
           This symbol will be defined if the C compiler supports "off64_t".

       "HAS_OPEN3"
           This manifest constant lets the C program know that the three
           argument form of open(2) is available.

       "HAS_OPENAT"
           This symbol is defined if the "openat()" routine is available.

       "HAS_POLL"
           This symbol, if defined, indicates that the "poll" routine is
           available to "poll" active file descriptors.  Please check "I_POLL"
           and "I_SYS_POLL" to know which header should be included as well.

       "HAS_READDIR"
           This symbol, if defined, indicates that the "readdir" routine is
           available to read directory entries. You may have to include
           dirent.h. See "I_DIRENT".

       "HAS_READDIR64_R"
           This symbol, if defined, indicates that the "readdir64_r" routine
           is available to readdir64 re-entrantly.

       "HAS_REWINDDIR"
           This symbol, if defined, indicates that the "rewinddir" routine is
           available. You may have to include dirent.h. See "I_DIRENT".

       "HAS_RMDIR"
           This symbol, if defined, indicates that the "rmdir" routine is
           available to remove directories. Otherwise you should fork off a
           new process to exec /bin/rmdir.

       "HAS_SEEKDIR"
           This symbol, if defined, indicates that the "seekdir" routine is
           available. You may have to include dirent.h. See "I_DIRENT".

       "HAS_SELECT"
           This symbol, if defined, indicates that the "select" routine is
           available to "select" active file descriptors. If the timeout field
           is used, sys/time.h may need to be included.

       "HAS_SETVBUF"
           This symbol, if defined, indicates that the "setvbuf" routine is
           available to change buffering on an open stdio stream.  to a line-
           buffered mode.

       "HAS_STDIO_STREAM_ARRAY"
           This symbol, if defined, tells that there is an array holding the
           stdio streams.

       "HAS_STRUCT_FS_DATA"
           This symbol, if defined, indicates that the "struct fs_data" to do
           "statfs()" is supported.

       "HAS_STRUCT_STATFS"
           This symbol, if defined, indicates that the "struct statfs" to do
           "statfs()" is supported.

       "HAS_STRUCT_STATFS_F_FLAGS"
           This symbol, if defined, indicates that the "struct statfs" does
           have the "f_flags" member containing the mount flags of the
           filesystem containing the file.  This kind of "struct statfs" is
           coming from sys/mount.h ("BSD" 4.3), not from sys/statfs.h
           ("SYSV").  Older "BSDs" (like Ultrix) do not have "statfs()" and
           "struct statfs", they have "ustat()" and "getmnt()" with "struct
           ustat" and "struct fs_data".

       "HAS_TELLDIR"
           This symbol, if defined, indicates that the "telldir" routine is
           available. You may have to include dirent.h. See "I_DIRENT".

       "HAS_USTAT"
           This symbol, if defined, indicates that the "ustat" system call is
           available to query file system statistics by "dev_t".

       "I_FCNTL"
           This manifest constant tells the C program to include fcntl.h.

            #ifdef I_FCNTL
                #include <fcntl.h>
            #endif

       "I_SYS_DIR"
           This symbol, if defined, indicates to the C program that it should
           include sys/dir.h.

            #ifdef I_SYS_DIR
                #include <sys_dir.h>
            #endif

       "I_SYS_FILE"
           This symbol, if defined, indicates to the C program that it should
           include sys/file.h to get definition of "R_OK" and friends.

            #ifdef I_SYS_FILE
                #include <sys_file.h>
            #endif

       "I_SYS_NDIR"
           This symbol, if defined, indicates to the C program that it should
           include sys/ndir.h.

            #ifdef I_SYS_NDIR
                #include <sys_ndir.h>
            #endif

       "I_SYS_STATFS"
           This symbol, if defined, indicates that sys/statfs.h exists.

            #ifdef I_SYS_STATFS
                #include <sys_statfs.h>
            #endif

       "LSEEKSIZE"
           This symbol holds the number of bytes used by the "Off_t".

       "RD_NODATA"
           This symbol holds the return code from "read()" when no data is
           present on the non-blocking file descriptor. Be careful! If
           "EOF_NONBLOCK" is not defined, then you can't distinguish between
           no data and "EOF" by issuing a "read()". You'll have to find
           another way to tell for sure!

       "READDIR64_R_PROTO"
           This symbol encodes the prototype of "readdir64_r".  It is zero if
           "d_readdir64_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_readdir64_r" is defined.

       "STDCHAR"
           This symbol is defined to be the type of char used in stdio.h.  It
           has the values "unsigned char" or "char".

       "STDIO_CNT_LVALUE"
           This symbol is defined if the "FILE_cnt" macro can be used as an
           lvalue.

       "STDIO_PTR_LVALUE"
           This symbol is defined if the "FILE_ptr" macro can be used as an
           lvalue.

       "STDIO_PTR_LVAL_NOCHANGE_CNT"
           This symbol is defined if using the "FILE_ptr" macro as an lvalue
           to increase the pointer by n leaves "File_cnt(fp)" unchanged.

       "STDIO_PTR_LVAL_SETS_CNT"
           This symbol is defined if using the "FILE_ptr" macro as an lvalue
           to increase the pointer by n has the side effect of decreasing the
           value of "File_cnt(fp)" by n.

       "STDIO_STREAM_ARRAY"
           This symbol tells the name of the array holding the stdio streams.
           Usual values include "_iob", "__iob", and "__sF".

       "ST_INO_SIGN"
           This symbol holds the signedness of "struct stat"'s "st_ino".  1
           for unsigned, -1 for signed.

       "ST_INO_SIZE"
           This variable contains the size of "struct stat"'s "st_ino" in
           bytes.

       "VAL_EAGAIN"
           This symbol holds the errno error code set by "read()" when no data
           was present on the non-blocking file descriptor.

       "VAL_O_NONBLOCK"
           This symbol is to be used during "open()" or "fcntl(F_SETFL)" to
           turn on non-blocking I/O for the file descriptor. Note that there
           is no way back, i.e. you cannot turn it blocking again this way. If
           you wish to alternatively switch between blocking and non-blocking,
           use the "ioctl(FIOSNBIO)" call instead, but that is not supported
           by all devices.

       "VOID_CLOSEDIR"
           This symbol, if defined, indicates that the "closedir()" routine
           does not return a value.


Floating point configuration values

       Also "List of capability HAS_foo symbols" lists capabilities that arent
       in this section.  For example "HAS_ASINH", for the hyperbolic sine
       function.

       "CASTFLAGS"
           This symbol contains flags that say what difficulties the compiler
           has casting odd floating values to unsigned long:

            0 = ok
            1 = couldn't cast < 0
            2 = couldn't cast >= 0x80000000
            4 = couldn't cast in argument expression list

       "CASTNEGFLOAT"
           This symbol is defined if the C compiler can cast negative numbers
           to unsigned longs, ints and shorts.

       "DOUBLE_HAS_INF"
           This symbol, if defined, indicates that the double has the
           infinity.

       "DOUBLE_HAS_NAN"
           This symbol, if defined, indicates that the double has the not-a-
           number.

       "DOUBLE_HAS_NEGATIVE_ZERO"
           This symbol, if defined, indicates that the double has the
           "negative_zero".

       "DOUBLE_HAS_SUBNORMALS"
           This symbol, if defined, indicates that the double has the
           subnormals (denormals).

       "DOUBLEINFBYTES"
           This symbol, if defined, is a comma-separated list of hexadecimal
           bytes for the double precision infinity.

       "DOUBLEKIND"
           "DOUBLEKIND" will be one of
           "DOUBLE_IS_IEEE_754_32_BIT_LITTLE_ENDIAN"
           "DOUBLE_IS_IEEE_754_32_BIT_BIG_ENDIAN"
           "DOUBLE_IS_IEEE_754_64_BIT_LITTLE_ENDIAN"
           "DOUBLE_IS_IEEE_754_64_BIT_BIG_ENDIAN"
           "DOUBLE_IS_IEEE_754_128_BIT_LITTLE_ENDIAN"
           "DOUBLE_IS_IEEE_754_128_BIT_BIG_ENDIAN"
           "DOUBLE_IS_IEEE_754_64_BIT_MIXED_ENDIAN_LE_BE"
           "DOUBLE_IS_IEEE_754_64_BIT_MIXED_ENDIAN_BE_LE"
           "DOUBLE_IS_VAX_F_FLOAT" "DOUBLE_IS_VAX_D_FLOAT"
           "DOUBLE_IS_VAX_G_FLOAT" "DOUBLE_IS_IBM_SINGLE_32_BIT"
           "DOUBLE_IS_IBM_DOUBLE_64_BIT" "DOUBLE_IS_CRAY_SINGLE_64_BIT"
           "DOUBLE_IS_UNKNOWN_FORMAT"

       "DOUBLEMANTBITS"
           This symbol, if defined, tells how many mantissa bits there are in
           double precision floating point format.  Note that this is usually
           "DBL_MANT_DIG" minus one, since with the standard "IEEE" 754
           formats "DBL_MANT_DIG" includes the implicit bit, which doesn't
           really exist.

       "DOUBLENANBYTES"
           This symbol, if defined, is a comma-separated list of hexadecimal
           bytes (0xHH) for the double precision not-a-number.

       "DOUBLESIZE"
           This symbol contains the size of a double, so that the C
           preprocessor can make decisions based on it.

       "DOUBLE_STYLE_CRAY"
           This symbol, if defined, indicates that the double is the 64-bit
           "CRAY" mainframe format.

       "DOUBLE_STYLE_IBM"
           This symbol, if defined, indicates that the double is the 64-bit
           "IBM" mainframe format.

       "DOUBLE_STYLE_IEEE"
           This symbol, if defined, indicates that the double is the 64-bit
           "IEEE" 754.

       "DOUBLE_STYLE_VAX"
           This symbol, if defined, indicates that the double is the 64-bit
           "VAX" format D or G.

       "HAS_ATOLF"
           This symbol, if defined, indicates that the "atolf" routine is
           available to convert strings into long doubles.

       "HAS_CLASS"
           This symbol, if defined, indicates that the "class" routine is
           available to classify doubles.  Available for example in "AIX".
           The returned values are defined in float.h and are:

            FP_PLUS_NORM    Positive normalized, nonzero
            FP_MINUS_NORM   Negative normalized, nonzero
            FP_PLUS_DENORM  Positive denormalized, nonzero
            FP_MINUS_DENORM Negative denormalized, nonzero
            FP_PLUS_ZERO    +0.0
            FP_MINUS_ZERO   -0.0
            FP_PLUS_INF     +INF
            FP_MINUS_INF    -INF
            FP_NANS         Signaling Not a Number (NaNS)
            FP_NANQ         Quiet Not a Number (NaNQ)

       "HAS_FINITE"
           This symbol, if defined, indicates that the "finite" routine is
           available to check whether a double is "finite" (non-infinity non-
           NaN).

       "HAS_FINITEL"
           This symbol, if defined, indicates that the "finitel" routine is
           available to check whether a long double is finite (non-infinity
           non-NaN).

       "HAS_FPCLASS"
           This symbol, if defined, indicates that the "fpclass" routine is
           available to classify doubles.  Available for example in
           Solaris/"SVR4".  The returned values are defined in ieeefp.h and
           are:

            FP_SNAN         signaling NaN
            FP_QNAN         quiet NaN
            FP_NINF         negative infinity
            FP_PINF         positive infinity
            FP_NDENORM      negative denormalized non-zero
            FP_PDENORM      positive denormalized non-zero
            FP_NZERO        negative zero
            FP_PZERO        positive zero
            FP_NNORM        negative normalized non-zero
            FP_PNORM        positive normalized non-zero

       "HAS_FPCLASSIFY"
           This symbol, if defined, indicates that the "fpclassify" routine is
           available to classify doubles.  Available for example in HP-UX.
           The returned values are defined in math.h and are

            FP_NORMAL     Normalized
            FP_ZERO       Zero
            FP_INFINITE   Infinity
            FP_SUBNORMAL  Denormalized
            FP_NAN        NaN

       "HAS_FPCLASSL"
           This symbol, if defined, indicates that the "fpclassl" routine is
           available to classify long doubles.  Available for example in
           "IRIX".  The returned values are defined in ieeefp.h and are:

            FP_SNAN         signaling NaN
            FP_QNAN         quiet NaN
            FP_NINF         negative infinity
            FP_PINF         positive infinity
            FP_NDENORM      negative denormalized non-zero
            FP_PDENORM      positive denormalized non-zero
            FP_NZERO        negative zero
            FP_PZERO        positive zero
            FP_NNORM        negative normalized non-zero
            FP_PNORM        positive normalized non-zero

       "HAS_FPGETROUND"
           This symbol, if defined, indicates that the "fpgetround" routine is
           available to get the floating point rounding mode.

       "HAS_FP_CLASS"
           This symbol, if defined, indicates that the "fp_class" routine is
           available to classify doubles.  Available for example in Digital
           "UNIX".  The returned values are defined in math.h and are:

            FP_SNAN           Signaling NaN (Not-a-Number)
            FP_QNAN           Quiet NaN (Not-a-Number)
            FP_POS_INF        +infinity
            FP_NEG_INF        -infinity
            FP_POS_NORM       Positive normalized
            FP_NEG_NORM       Negative normalized
            FP_POS_DENORM     Positive denormalized
            FP_NEG_DENORM     Negative denormalized
            FP_POS_ZERO       +0.0 (positive zero)
            FP_NEG_ZERO       -0.0 (negative zero)

       "HAS_FP_CLASSIFY"
           This symbol, if defined, indicates that the "fp_classify" routine
           is available to classify doubles. The values are defined in math.h

            FP_NORMAL     Normalized
            FP_ZERO       Zero
            FP_INFINITE   Infinity
            FP_SUBNORMAL  Denormalized
            FP_NAN        NaN

       "HAS_FP_CLASSL"
           This symbol, if defined, indicates that the "fp_classl" routine is
           available to classify long doubles.  Available for example in
           Digital "UNIX".  See for possible values "HAS_FP_CLASS".

       "HAS_FREXPL"
           This symbol, if defined, indicates that the "frexpl" routine is
           available to break a long double floating-point number into a
           normalized fraction and an integral power of 2.

       "HAS_ILOGB"
           This symbol, if defined, indicates that the "ilogb" routine is
           available to get integer exponent of a floating-point value.

       "HAS_ISFINITE"
           This symbol, if defined, indicates that the "isfinite" routine is
           available to check whether a double is finite (non-infinity non-
           NaN).

       "HAS_ISFINITEL"
           This symbol, if defined, indicates that the "isfinitel" routine is
           available to check whether a long double is finite.  (non-infinity
           non-NaN).

       "HAS_ISINF"
           This symbol, if defined, indicates that the "isinf" routine is
           available to check whether a double is an infinity.

       "HAS_ISINFL"
           This symbol, if defined, indicates that the "isinfl" routine is
           available to check whether a long double is an infinity.

       "HAS_ISNAN"
           This symbol, if defined, indicates that the "isnan" routine is
           available to check whether a double is a NaN.

       "HAS_ISNANL"
           This symbol, if defined, indicates that the "isnanl" routine is
           available to check whether a long double is a NaN.

       "HAS_ISNORMAL"
           This symbol, if defined, indicates that the "isnormal" routine is
           available to check whether a double is normal (non-zero
           normalized).

       "HAS_J0"
           This symbol, if defined, indicates to the C program that the "j0()"
           function is available for Bessel functions of the first kind of the
           order zero, for doubles.

       "HAS_J0L"
           This symbol, if defined, indicates to the C program that the
           "j0l()" function is available for Bessel functions of the first
           kind of the order zero, for long doubles.

       "HAS_LDBL_DIG"
           This symbol, if defined, indicates that this system's float.h or
           limits.h defines the symbol "LDBL_DIG", which is the number of
           significant digits in a long double precision number. Unlike for
           "DBL_DIG", there's no good guess for "LDBL_DIG" if it is undefined.

       "HAS_LDEXPL"
           This symbol, if defined, indicates that the "ldexpl" routine is
           available to shift a long double floating-point number by an
           integral power of 2.

       "HAS_LLRINT"
           This symbol, if defined, indicates that the "llrint" routine is
           available to return the long long value closest to a double
           (according to the current rounding mode).

       "HAS_LLRINTL"
           This symbol, if defined, indicates that the "llrintl" routine is
           available to return the long long value closest to a long double
           (according to the current rounding mode).

       "HAS_LLROUNDL"
           This symbol, if defined, indicates that the "llroundl" routine is
           available to return the nearest long long value away from zero of
           the long double argument value.

       "HAS_LONG_DOUBLE"
           This symbol will be defined if the C compiler supports long
           doubles.

       "HAS_LRINT"
           This symbol, if defined, indicates that the "lrint" routine is
           available to return the integral value closest to a double
           (according to the current rounding mode).

       "HAS_LRINTL"
           This symbol, if defined, indicates that the "lrintl" routine is
           available to return the integral value closest to a long double
           (according to the current rounding mode).

       "HAS_LROUNDL"
           This symbol, if defined, indicates that the "lroundl" routine is
           available to return the nearest integral value away from zero of
           the long double argument value.

       "HAS_MODFL"
           This symbol, if defined, indicates that the "modfl" routine is
           available to split a long double x into a fractional part f and an
           integer part i such that |f| < 1.0 and (f + i) = x.

       "HAS_NAN"
           This symbol, if defined, indicates that the "nan" routine is
           available to generate NaN.

       "HAS_NEXTTOWARD"
           This symbol, if defined, indicates that the "nexttoward" routine is
           available to return the next machine representable long double from
           x in direction y.

       "HAS_REMAINDER"
           This symbol, if defined, indicates that the "remainder" routine is
           available to return the floating-point "remainder".

       "HAS_SCALBN"
           This symbol, if defined, indicates that the "scalbn" routine is
           available to multiply floating-point number by integral power of
           radix.

       "HAS_SIGNBIT"
           This symbol, if defined, indicates that the "signbit" routine is
           available to check if the given number has the sign bit set.  This
           should include correct testing of -0.0.  This will only be set if
           the "signbit()" routine is safe to use with the NV type used
           internally in perl.  Users should call "Perl_signbit()", which will
           be #defined to the system's "signbit()" function or macro if this
           symbol is defined.

       "HAS_SQRTL"
           This symbol, if defined, indicates that the "sqrtl" routine is
           available to do long double square roots.

       "HAS_STRTOD_L"
           This symbol, if defined, indicates that the "strtod_l" routine is
           available to convert strings to long doubles.

       "HAS_STRTOLD"
           This symbol, if defined, indicates that the "strtold" routine is
           available to convert strings to long doubles.

       "HAS_STRTOLD_L"
           This symbol, if defined, indicates that the "strtold_l" routine is
           available to convert strings to long doubles.

       "HAS_TRUNC"
           This symbol, if defined, indicates that the "trunc" routine is
           available to round doubles towards zero.

       "HAS_UNORDERED"
           This symbol, if defined, indicates that the "unordered" routine is
           available to check whether two doubles are "unordered"
           (effectively: whether either of them is NaN)

       "I_FENV"
           This symbol, if defined, indicates to the C program that it should
           include fenv.h to get the floating point environment definitions.

            #ifdef I_FENV
                #include <fenv.h>
            #endif

       "I_QUADMATH"
           This symbol, if defined, indicates that quadmath.h exists and
           should be included.

            #ifdef I_QUADMATH
                #include <quadmath.h>
            #endif

       "LONGDBLINFBYTES"
           This symbol, if defined, is a comma-separated list of hexadecimal
           bytes for the long double precision infinity.

       "LONGDBLMANTBITS"
           This symbol, if defined, tells how many mantissa bits there are in
           long double precision floating point format.  Note that this can be
           "LDBL_MANT_DIG" minus one, since "LDBL_MANT_DIG" can include the
           "IEEE" 754 implicit bit.  The common x86-style 80-bit long double
           does not have an implicit bit.

       "LONGDBLNANBYTES"
           This symbol, if defined, is a comma-separated list of hexadecimal
           bytes (0xHH) for the long double precision not-a-number.

       "LONG_DOUBLEKIND"
           "LONG_DOUBLEKIND" will be one of "LONG_DOUBLE_IS_DOUBLE"
           "LONG_DOUBLE_IS_IEEE_754_128_BIT_LITTLE_ENDIAN"
           "LONG_DOUBLE_IS_IEEE_754_128_BIT_BIG_ENDIAN"
           "LONG_DOUBLE_IS_X86_80_BIT_LITTLE_ENDIAN"
           "LONG_DOUBLE_IS_X86_80_BIT_BIG_ENDIAN"
           "LONG_DOUBLE_IS_DOUBLEDOUBLE_128_BIT_LE_LE"
           "LONG_DOUBLE_IS_DOUBLEDOUBLE_128_BIT_BE_BE"
           "LONG_DOUBLE_IS_DOUBLEDOUBLE_128_BIT_LE_BE"
           "LONG_DOUBLE_IS_DOUBLEDOUBLE_128_BIT_BE_LE"
           "LONG_DOUBLE_IS_DOUBLEDOUBLE_128_BIT_LITTLE_ENDIAN"
           "LONG_DOUBLE_IS_DOUBLEDOUBLE_128_BIT_BIG_ENDIAN"
           "LONG_DOUBLE_IS_VAX_H_FLOAT" "LONG_DOUBLE_IS_UNKNOWN_FORMAT" It is
           only defined if the system supports long doubles.

       "LONG_DOUBLESIZE"
           This symbol contains the size of a long double, so that the C
           preprocessor can make decisions based on it.  It is only defined if
           the system supports long doubles.  Note that this is "sizeof(long
           double)", which may include unused bytes.

       "LONG_DOUBLE_STYLE_IEEE"
           This symbol, if defined, indicates that the long double is any of
           the "IEEE" 754 style long doubles: "LONG_DOUBLE_STYLE_IEEE_STD",
           "LONG_DOUBLE_STYLE_IEEE_EXTENDED",
           "LONG_DOUBLE_STYLE_IEEE_DOUBLEDOUBLE".

       "LONG_DOUBLE_STYLE_IEEE_DOUBLEDOUBLE"
           This symbol, if defined, indicates that the long double is the
           128-bit double-double.

       "LONG_DOUBLE_STYLE_IEEE_EXTENDED"
           This symbol, if defined, indicates that the long double is the
           80-bit "IEEE" 754. Note that despite the 'extended' this is less
           than the 'std', since this is an extension of the double precision.

       "LONG_DOUBLE_STYLE_IEEE_STD"
           This symbol, if defined, indicates that the long double is the
           128-bit "IEEE" 754.

       "LONG_DOUBLE_STYLE_VAX"
           This symbol, if defined, indicates that the long double is the
           128-bit "VAX" format H.

       "NVMANTBITS"
           This symbol, if defined, tells how many mantissa bits (not
           including implicit bit) there are in a Perl NV.  This depends on
           which floating point type was chosen.

       "NV_OVERFLOWS_INTEGERS_AT"
           This symbol gives the largest integer value that NVs can hold. This
           value + 1.0 cannot be stored accurately. It is expressed as
           constant floating point expression to reduce the chance of
           decimal/binary conversion issues. If it can not be determined, the
           value 0 is given.

       "NV_PRESERVES_UV"
           This symbol, if defined, indicates that a variable of type "NVTYPE"
           can preserve all the bits of a variable of type "UVTYPE".

       "NV_PRESERVES_UV_BITS"
           This symbol contains the number of bits a variable of type "NVTYPE"
           can preserve of a variable of type "UVTYPE".

       "NVSIZE"
           This symbol contains the "sizeof(NV)".  Note that some floating
           point formats have unused bytes.  The most notable example is the
           x86* 80-bit extended precision which comes in byte sizes of 12 and
           16 (for 32 and 64 bit platforms, respectively), but which only uses
           10 bytes.  Perl compiled with "-Duselongdouble" on x86* is like
           this.

       "NVTYPE"
           This symbol defines the C type used for Perl's NV.

       "NV_ZERO_IS_ALLBITS_ZERO"
           This symbol, if defined, indicates that a variable of type "NVTYPE"
           stores 0.0 in memory as all bits zero.


Formats

       These are used for formatting the corresponding type For example,
       instead of saying

        Perl_newSVpvf(pTHX_ "Create an SV with a %d in it\n", iv);

       use

        Perl_newSVpvf(pTHX_ "Create an SV with a " IVdf " in it\n", iv);

       This keeps you from having to know if, say an IV, needs to be printed
       as %d, %ld, or something else.

       "IVdf"
           This symbol defines the format string used for printing a Perl IV
           as a signed decimal integer.

       "NVef"
           This symbol defines the format string used for printing a Perl NV
           using %e-ish floating point format.

       "NVff"
           This symbol defines the format string used for printing a Perl NV
           using %f-ish floating point format.

       "NVgf"
           This symbol defines the format string used for printing a Perl NV
           using %g-ish floating point format.

       "PERL_PRIeldbl"
           This symbol, if defined, contains the string used by stdio to
           format long doubles (format 'e') for output.

       "PERL_PRIfldbl"
           This symbol, if defined, contains the string used by stdio to
           format long doubles (format 'f') for output.

       "PERL_PRIgldbl"
           This symbol, if defined, contains the string used by stdio to
           format long doubles (format 'g') for output.

       "PERL_SCNfldbl"
           This symbol, if defined, contains the string used by stdio to
           format long doubles (format 'f') for input.

       "PRINTF_FORMAT_NULL_OK"
           Allows "__printf__" format to be null when checking printf-style

       "UTF8f"
           Described in perlguts.

       "UTF8fARG"
           Described in perlguts.

              UTF8fARG(bool is_utf8, Size_t byte_len, char *str)

       "UVof"
           This symbol defines the format string used for printing a Perl UV
           as an unsigned octal integer.

       "UVuf"
           This symbol defines the format string used for printing a Perl UV
           as an unsigned decimal integer.

       "UVXf"
           This symbol defines the format string used for printing a Perl UV
           as an unsigned hexadecimal integer in uppercase "ABCDEF".

       "UVxf"
           This symbol defines the format string used for printing a Perl UV
           as an unsigned hexadecimal integer in lowercase abcdef.


General Configuration

       This section contains configuration information not otherwise found in
       the more specialized sections of this document.  At the end is a list
       of "#defines" whose name should be enough to tell you what they do, and
       a list of #defines which tell you if you need to "#include" files to
       get the corresponding functionality.

       "BYTEORDER"
           This symbol holds the hexadecimal constant defined in byteorder, in
           a UV, i.e. 0x1234 or 0x4321 or 0x12345678, etc...  If the compiler
           supports cross-compiling or multiple-architecture binaries, use
           compiler-defined macros to determine the byte order.

       "CHARBITS"
           This symbol contains the size of a char, so that the C preprocessor
           can make decisions based on it.

       "DB_VERSION_MAJOR_CFG"
           This symbol, if defined, defines the major version number of
           Berkeley DB found in the db.h header when Perl was configured.

       "DB_VERSION_MINOR_CFG"
           This symbol, if defined, defines the minor version number of
           Berkeley DB found in the db.h header when Perl was configured.  For
           DB version 1 this is always 0.

       "DB_VERSION_PATCH_CFG"
           This symbol, if defined, defines the patch version number of
           Berkeley DB found in the db.h header when Perl was configured.  For
           DB version 1 this is always 0.

       "DEFAULT_INC_EXCLUDES_DOT"
           This symbol, if defined, removes the legacy default behavior of
           including '.' at the end of @"INC".

       "DLSYM_NEEDS_UNDERSCORE"
           This symbol, if defined, indicates that we need to prepend an
           underscore to the symbol name before calling "dlsym()".  This only
           makes sense if you *have* dlsym, which we will presume is the case
           if you're using dl_dlopen.xs.

       "EBCDIC"
           This symbol, if defined, indicates that this system uses "EBCDIC"
           encoding.

       "HAS_CSH"
           This symbol, if defined, indicates that the C-shell exists.

       "HAS_GETHOSTNAME"
           This symbol, if defined, indicates that the C program may use the
           "gethostname()" routine to derive the host name.  See also
           "HAS_UNAME" and "PHOSTNAME".

       "HAS_GNULIBC"
           This symbol, if defined, indicates to the C program that the "GNU"
           C library is being used.  A better check is to use the "__GLIBC__"
           and "__GLIBC_MINOR__" symbols supplied with glibc.

       "HAS_LGAMMA"
           This symbol, if defined, indicates that the "lgamma" routine is
           available to do the log gamma function.  See also "HAS_TGAMMA" and
           "HAS_LGAMMA_R".

       "HAS_LGAMMA_R"
           This symbol, if defined, indicates that the "lgamma_r" routine is
           available to do the log gamma function without using the global
           signgam variable.

       "HAS_PRCTL_SET_NAME"
           This symbol, if defined, indicates that the prctl routine is
           available to set process title and supports "PR_SET_NAME".

       "HAS_PROCSELFEXE"
           This symbol is defined if "PROCSELFEXE_PATH" is a symlink to the
           absolute pathname of the executing program.

       "HAS_PSEUDOFORK"
           This symbol, if defined, indicates that an emulation of the fork
           routine is available.

       "HAS_REGCOMP"
           This symbol, if defined, indicates that the "regcomp()" routine is
           available to do some regular pattern matching (usually on "POSIX".2
           conforming systems).

       "HAS_SETPGID"
           This symbol, if defined, indicates that the "setpgid(pid, gpid)"
           routine is available to set process group ID.

       "HAS_SIGSETJMP"
           This variable indicates to the C program that the "sigsetjmp()"
           routine is available to save the calling process's registers and
           stack environment for later use by "siglongjmp()", and to
           optionally save the process's signal mask.  See "Sigjmp_buf",
           "Sigsetjmp", and "Siglongjmp".

       "HAS_STRUCT_CMSGHDR"
           This symbol, if defined, indicates that the "struct cmsghdr" is
           supported.

       "HAS_STRUCT_MSGHDR"
           This symbol, if defined, indicates that the "struct msghdr" is
           supported.

       "HAS_TGAMMA"
           This symbol, if defined, indicates that the "tgamma" routine is
           available to do the gamma function. See also "HAS_LGAMMA".

       "HAS_UNAME"
           This symbol, if defined, indicates that the C program may use the
           "uname()" routine to derive the host name.  See also
           "HAS_GETHOSTNAME" and "PHOSTNAME".

       "HAS_UNION_SEMUN"
           This symbol, if defined, indicates that the "union semun" is
           defined by including sys/sem.h.  If not, the user code probably
           needs to define it as:

            union semun {
            int val;
            struct semid_ds *buf;
            unsigned short *array;
            }

       "I_DIRENT"
           This symbol, if defined, indicates to the C program that it should
           include dirent.h. Using this symbol also triggers the definition of
           the "Direntry_t" define which ends up being '"struct dirent"' or
           '"struct direct"' depending on the availability of dirent.h.

            #ifdef I_DIRENT
                #include <dirent.h>
            #endif

       "I_POLL"
           This symbol, if defined, indicates that poll.h exists and should be
           included. (see also "HAS_POLL")

            #ifdef I_POLL
                #include <poll.h>
            #endif

       "I_SYS_RESOURCE"
           This symbol, if defined, indicates to the C program that it should
           include sys/resource.h.

            #ifdef I_SYS_RESOURCE
                #include <sys_resource.h>
            #endif

       "LIBM_LIB_VERSION"
           This symbol, if defined, indicates that libm exports "_LIB_VERSION"
           and that math.h defines the enum to manipulate it.

       "NEED_VA_COPY"
           This symbol, if defined, indicates that the system stores the
           variable argument list datatype, "va_list", in a format that cannot
           be copied by simple assignment, so that some other means must be
           used when copying is required.  As such systems vary in their
           provision (or non-provision) of copying mechanisms, handy.h defines
           a platform- independent macro, "Perl_va_copy(src, dst)", to do the
           job.

       "OSNAME"
           This symbol contains the name of the operating system, as
           determined by Configure.  You shouldn't rely on it too much; the
           specific feature tests from Configure are generally more reliable.

       "OSVERS"
           This symbol contains the version of the operating system, as
           determined by Configure.  You shouldn't rely on it too much; the
           specific feature tests from Configure are generally more reliable.

       "PHOSTNAME"
           This symbol, if defined, indicates the command to feed to the
           "popen()" routine to derive the host name.  See also
           "HAS_GETHOSTNAME" and "HAS_UNAME".  Note that the command uses a
           fully qualified path, so that it is safe even if used by a process
           with super-user privileges.

       "PROCSELFEXE_PATH"
           If "HAS_PROCSELFEXE" is defined this symbol is the filename of the
           symbolic link pointing to the absolute pathname of the executing
           program.

       "PTRSIZE"
           This symbol contains the size of a pointer, so that the C
           preprocessor can make decisions based on it.  It will be
           "sizeof(void *)" if the compiler supports (void *); otherwise it
           will be "sizeof(char *)".

       "RANDBITS"
           This symbol indicates how many bits are produced by the function
           used to generate normalized random numbers.  Values include 15, 16,
           31, and 48.

       "SELECT_MIN_BITS"
           This symbol holds the minimum number of bits operated by select.
           That is, if you do "select(n, ...)", how many bits at least will be
           cleared in the masks if some activity is detected.  Usually this is
           either n or 32*"ceil(n/32)", especially many little-endians do the
           latter.  This is only useful if you have "select()", naturally.

       "SETUID_SCRIPTS_ARE_SECURE_NOW"
           This symbol, if defined, indicates that the bug that prevents
           setuid scripts from being secure is not present in this kernel.

   List of capability "HAS_foo" symbols
       This is a list of those symbols that dont appear elsewhere in ths
       document that indicate if the current platform has a certain
       capability.  Their names all begin with "HAS_".  Only those symbols
       whose capability is directly derived from the name are listed here.
       All others have their meaning expanded out elsewhere in this document.
       This (relatively) compact list is because we think that the expansion
       would add little or no value and take up a lot of space (because there
       are so many).  If you think certain ones should be expanded, send email
       to perl5-porters@perl.org <mailto:perl5-porters@perl.org>.

       Each symbol here will be "#define"d if and only if the platform has the
       capability.  If you need more detail, see the corresponding entry in
       config.h.  For convenience, the list is split so that the ones that
       indicate there is a reentrant version of a capability are listed
       separately

       "HAS_ACCEPT4",  "HAS_ACCESS",  "HAS_ACCESSX",  "HAS_ACOSH",
       "HAS_AINTL",  "HAS_ALARM",  "HAS_ASINH",  "HAS_ATANH",  "HAS_ATOLL",
       "HAS_CBRT",  "HAS_CHOWN",  "HAS_CHROOT",  "HAS_CHSIZE",
       "HAS_CLEARENV",  "HAS_COPYSIGN",  "HAS_COPYSIGNL",  "HAS_CRYPT",
       "HAS_CTERMID",  "HAS_CUSERID",  "HAS_DIRFD",  "HAS_DLADDR",
       "HAS_DLERROR",  "HAS_EACCESS",  "HAS_ENDHOSTENT",  "HAS_ENDNETENT",
       "HAS_ENDPROTOENT",  "HAS_ENDSERVENT",  "HAS_ERF",  "HAS_ERFC",
       "HAS_EXP2",  "HAS_EXPM1",  "HAS_FCHMOD",  "HAS_FCHMODAT",
       "HAS_FCHOWN",  "HAS_FDIM",  "HAS_FD_SET",  "HAS_FEGETROUND",
       "HAS_FGETPOS",  "HAS_FLOCK",  "HAS_FMA",  "HAS_FMAX",  "HAS_FMIN",
       "HAS_FORK",  "HAS_FSEEKO",  "HAS_FSETPOS",  "HAS_FSYNC",
       "HAS_FTELLO",  "HAS_GAI_STRERROR",  "HAS_GETADDRINFO",  "HAS_GETCWD",
       "HAS_GETESPWNAM",  "HAS_GETGROUPS",  "HAS_GETHOSTBYADDR",
       "HAS_GETHOSTBYNAME",  "HAS_GETHOSTENT",  "HAS_GETLOGIN",
       "HAS_GETNAMEINFO",  "HAS_GETNETBYADDR",  "HAS_GETNETBYNAME",
       "HAS_GETNETENT",  "HAS_GETPAGESIZE",  "HAS_GETPGID",  "HAS_GETPGRP",
       "HAS_GETPGRP2",  "HAS_GETPPID",  "HAS_GETPRIORITY",
       "HAS_GETPROTOBYNAME",  "HAS_GETPROTOBYNUMBER",  "HAS_GETPROTOENT",
       "HAS_GETPRPWNAM",  "HAS_GETSERVBYNAME",  "HAS_GETSERVBYPORT",
       "HAS_GETSERVENT",  "HAS_GETSPNAM",  "HAS_HTONL",  "HAS_HTONS",
       "HAS_HYPOT",  "HAS_ILOGBL",  "HAS_INETNTOP",  "HAS_INETPTON",
       "HAS_INET_ATON",  "HAS_IPV6_MREQ",  "HAS_IPV6_MREQ_SOURCE",
       "HAS_IP_MREQ",  "HAS_IP_MREQ_SOURCE",  "HAS_ISASCII",  "HAS_ISBLANK",
       "HAS_ISLESS",  "HAS_KILLPG",  "HAS_LCHOWN",  "HAS_LINK",
       "HAS_LINKAT",  "HAS_LLROUND",  "HAS_LOCKF",  "HAS_LOG1P",  "HAS_LOG2",
       "HAS_LOGB",  "HAS_LROUND",  "HAS_LSTAT",  "HAS_MADVISE",  "HAS_MBLEN",
       "HAS_MBRLEN",  "HAS_MBRTOWC",  "HAS_MBSTOWCS",  "HAS_MBTOWC",
       "HAS_MEMMEM",  "HAS_MEMRCHR",  "HAS_MKDTEMP",  "HAS_MKFIFO",
       "HAS_MKOSTEMP",  "HAS_MKSTEMP",  "HAS_MKSTEMPS",  "HAS_MMAP",
       "HAS_MPROTECT",  "HAS_MSG",  "HAS_MSYNC",  "HAS_MUNMAP",
       "HAS_NEARBYINT",  "HAS_NEXTAFTER",  "HAS_NICE",  "HAS_NTOHL",
       "HAS_NTOHS",  "HAS_PATHCONF",  "HAS_PAUSE",  "HAS_PHOSTNAME",
       "HAS_PIPE",  "HAS_PIPE2",  "HAS_PRCTL",  "HAS_PTRDIFF_T",
       "HAS_READLINK",  "HAS_READV",  "HAS_RECVMSG",  "HAS_REMQUO",
       "HAS_RENAME",  "HAS_RENAMEAT",  "HAS_RINT",  "HAS_ROUND",
       "HAS_SCALBNL",  "HAS_SEM",  "HAS_SENDMSG",  "HAS_SETEGID",
       "HAS_SETEUID",  "HAS_SETGROUPS",  "HAS_SETHOSTENT",  "HAS_SETLINEBUF",
       "HAS_SETNETENT",  "HAS_SETPGRP",  "HAS_SETPGRP2",  "HAS_SETPRIORITY",
       "HAS_SETPROCTITLE",  "HAS_SETPROTOENT",  "HAS_SETREGID",
       "HAS_SETRESGID",  "HAS_SETRESUID",  "HAS_SETREUID",  "HAS_SETRGID",
       "HAS_SETRUID",  "HAS_SETSERVENT",  "HAS_SETSID",  "HAS_SHM",
       "HAS_SIGACTION",  "HAS_SIGPROCMASK",  "HAS_SIN6_SCOPE_ID",
       "HAS_SNPRINTF",  "HAS_STAT",  "HAS_STRCOLL",  "HAS_STRERROR_L",
       "HAS_STRLCAT",  "HAS_STRLCPY",  "HAS_STRNLEN",  "HAS_STRTOD",
       "HAS_STRTOL",  "HAS_STRTOLL",  "HAS_STRTOQ",  "HAS_STRTOUL",
       "HAS_STRTOULL",  "HAS_STRTOUQ",  "HAS_STRXFRM",  "HAS_SYMLINK",
       "HAS_SYSCALL",  "HAS_SYSCONF",  "HAS_SYSTEM",  "HAS_SYS_ERRLIST",
       "HAS_TCGETPGRP",  "HAS_TCSETPGRP",  "HAS_TOWLOWER",  "HAS_TOWUPPER",
       "HAS_TRUNCATE",  "HAS_TRUNCL",  "HAS_UALARM",  "HAS_UMASK",
       "HAS_UNLINKAT",  "HAS_UNSETENV",  "HAS_VFORK",  "HAS_VSNPRINTF",
       "HAS_WAIT4",  "HAS_WAITPID",  "HAS_WCRTOMB",  "HAS_WCSCMP",
       "HAS_WCSTOMBS",  "HAS_WCSXFRM",  "HAS_WCTOMB",  "HAS_WRITEV",
       "HAS__FWALK"

       And, the reentrant capabilities:

       "HAS_CRYPT_R",  "HAS_CTERMID_R",  "HAS_DRAND48_R",
       "HAS_ENDHOSTENT_R",  "HAS_ENDNETENT_R",  "HAS_ENDPROTOENT_R",
       "HAS_ENDSERVENT_R",  "HAS_GETGRGID_R",  "HAS_GETGRNAM_R",
       "HAS_GETHOSTBYADDR_R",  "HAS_GETHOSTBYNAME_R",  "HAS_GETHOSTENT_R",
       "HAS_GETLOGIN_R",  "HAS_GETNETBYADDR_R",  "HAS_GETNETBYNAME_R",
       "HAS_GETNETENT_R",  "HAS_GETPROTOBYNAME_R",  "HAS_GETPROTOBYNUMBER_R",
       "HAS_GETPROTOENT_R",  "HAS_GETPWNAM_R",  "HAS_GETPWUID_R",
       "HAS_GETSERVBYNAME_R",  "HAS_GETSERVBYPORT_R",  "HAS_GETSERVENT_R",
       "HAS_GETSPNAM_R",  "HAS_RANDOM_R",  "HAS_READDIR_R",
       "HAS_SETHOSTENT_R",  "HAS_SETNETENT_R",  "HAS_SETPROTOENT_R",
       "HAS_SETSERVENT_R",  "HAS_SRAND48_R",  "HAS_SRANDOM_R",
       "HAS_STRERROR_R",  "HAS_TMPNAM_R",  "HAS_TTYNAME_R"

       Example usage:

        #ifdef HAS_STRNLEN
          use strnlen()
        #else
          use an alternative implementation
        #endif

   List of "#include" needed symbols
       This list contains symbols that indicate if certain "#include" files
       are present on the platform.  If your code accesses the functionality
       that one of these is for, you will need to "#include" it if the symbol
       on this list is "#define"d.  For more detail, see the corresponding
       entry in config.h.

       "I_ARPA_INET",  "I_BFD",  "I_CRYPT",  "I_DBM",  "I_DLFCN",
       "I_EXECINFO",  "I_FP",  "I_FP_CLASS",  "I_GDBM",  "I_GDBMNDBM",
       "I_GDBM_NDBM",  "I_GRP",  "I_IEEEFP",  "I_INTTYPES",  "I_LIBUTIL",
       "I_MNTENT",  "I_NDBM",  "I_NETDB",  "I_NETINET_IN",  "I_NETINET_TCP",
       "I_NET_ERRNO",  "I_PROT",  "I_PWD",  "I_RPCSVC_DBM",  "I_SGTTY",
       "I_SHADOW",  "I_STDBOOL",  "I_STDINT",  "I_SUNMATH",  "I_SYSLOG",
       "I_SYSMODE",  "I_SYSUIO",  "I_SYSUTSNAME",  "I_SYS_ACCESS",
       "I_SYS_IOCTL",  "I_SYS_MOUNT",  "I_SYS_PARAM",  "I_SYS_POLL",
       "I_SYS_SECURITY",  "I_SYS_SELECT",  "I_SYS_STAT",  "I_SYS_STATVFS",
       "I_SYS_TIME",  "I_SYS_TIMES",  "I_SYS_TIME_KERNEL",  "I_SYS_TYPES",
       "I_SYS_UN",  "I_SYS_VFS",  "I_SYS_WAIT",  "I_TERMIO",  "I_TERMIOS",
       "I_UNISTD",  "I_USTAT",  "I_VFORK",  "I_WCHAR",  "I_WCTYPE"

       Example usage:

        #ifdef I_WCHAR
          #include <wchar.h>
        #endif


Global Variables

       These variables are global to an entire process.  They are shared
       between all interpreters and all threads in a process.  Any variables
       not documented here may be changed or removed without notice, so don't
       use them!  If you feel you really do need to use an unlisted variable,
       first send email to perl5-porters@perl.org
       <mailto:perl5-porters@perl.org>.  It may be that someone there will
       point out a way to accomplish what you need without using an internal
       variable.  But if not, you should get a go-ahead to document and then
       use the variable.

       "PL_check"
           Array, indexed by opcode, of functions that will be called for the
           "check" phase of optree building during compilation of Perl code.
           For most (but not all) types of op, once the op has been initially
           built and populated with child ops it will be filtered through the
           check function referenced by the appropriate element of this array.
           The new op is passed in as the sole argument to the check function,
           and the check function returns the completed op.  The check
           function may (as the name suggests) check the op for validity and
           signal errors.  It may also initialise or modify parts of the ops,
           or perform more radical surgery such as adding or removing child
           ops, or even throw the op away and return a different op in its
           place.

           This array of function pointers is a convenient place to hook into
           the compilation process.  An XS module can put its own custom check
           function in place of any of the standard ones, to influence the
           compilation of a particular type of op.  However, a custom check
           function must never fully replace a standard check function (or
           even a custom check function from another module).  A module
           modifying checking must instead wrap the preexisting check
           function.  A custom check function must be selective about when to
           apply its custom behaviour.  In the usual case where it decides not
           to do anything special with an op, it must chain the preexisting op
           function.  Check functions are thus linked in a chain, with the
           core's base checker at the end.

           For thread safety, modules should not write directly to this array.
           Instead, use the function "wrap_op_checker".

       "PL_keyword_plugin"
           NOTE: "PL_keyword_plugin" is experimental and may change or be
           removed without notice.

           Function pointer, pointing at a function used to handle extended
           keywords.  The function should be declared as

                   int keyword_plugin_function(pTHX_
                           char *keyword_ptr, STRLEN keyword_len,
                           OP **op_ptr)

           The function is called from the tokeniser, whenever a possible
           keyword is seen.  "keyword_ptr" points at the word in the parser's
           input buffer, and "keyword_len" gives its length; it is not null-
           terminated.  The function is expected to examine the word, and
           possibly other state such as %^H, to decide whether it wants to
           handle it as an extended keyword.  If it does not, the function
           should return "KEYWORD_PLUGIN_DECLINE", and the normal parser
           process will continue.

           If the function wants to handle the keyword, it first must parse
           anything following the keyword that is part of the syntax
           introduced by the keyword.  See "Lexer interface" for details.

           When a keyword is being handled, the plugin function must build a
           tree of "OP" structures, representing the code that was parsed.
           The root of the tree must be stored in *op_ptr.  The function then
           returns a constant indicating the syntactic role of the construct
           that it has parsed: "KEYWORD_PLUGIN_STMT" if it is a complete
           statement, or "KEYWORD_PLUGIN_EXPR" if it is an expression.  Note
           that a statement construct cannot be used inside an expression
           (except via "do BLOCK" and similar), and an expression is not a
           complete statement (it requires at least a terminating semicolon).

           When a keyword is handled, the plugin function may also have
           (compile-time) side effects.  It may modify "%^H", define
           functions, and so on.  Typically, if side effects are the main
           purpose of a handler, it does not wish to generate any ops to be
           included in the normal compilation.  In this case it is still
           required to supply an op tree, but it suffices to generate a single
           null op.

           That's how the *PL_keyword_plugin function needs to behave overall.
           Conventionally, however, one does not completely replace the
           existing handler function.  Instead, take a copy of
           "PL_keyword_plugin" before assigning your own function pointer to
           it.  Your handler function should look for keywords that it is
           interested in and handle those.  Where it is not interested, it
           should call the saved plugin function, passing on the arguments it
           received.  Thus "PL_keyword_plugin" actually points at a chain of
           handler functions, all of which have an opportunity to handle
           keywords, and only the last function in the chain (built into the
           Perl core) will normally return "KEYWORD_PLUGIN_DECLINE".

           For thread safety, modules should not set this variable directly.
           Instead, use the function "wrap_keyword_plugin".

       "PL_phase"
           A value that indicates the current Perl interpreter's phase.
           Possible values include "PERL_PHASE_CONSTRUCT", "PERL_PHASE_START",
           "PERL_PHASE_CHECK", "PERL_PHASE_INIT", "PERL_PHASE_RUN",
           "PERL_PHASE_END", and "PERL_PHASE_DESTRUCT".

           For example, the following determines whether the interpreter is in
           global destruction:

               if (PL_phase == PERL_PHASE_DESTRUCT) {
                   // we are in global destruction
               }

           "PL_phase" was introduced in Perl 5.14; in prior perls you can use
           "PL_dirty" (boolean) to determine whether the interpreter is in
           global destruction. (Use of "PL_dirty" is discouraged since 5.14.)

            enum perl_phase  PL_phase


GV Handling

       A GV is a structure which corresponds to to a Perl typeglob, ie *foo.
       It is a structure that holds a pointer to a scalar, an array, a hash
       etc, corresponding to $foo, @foo, %foo.

       GVs are usually found as values in stashes (symbol table hashes) where
       Perl stores its global variables.

       "gv_autoload4"
           Equivalent to "gv_autoload_pvn".

            GV*  gv_autoload4(HV* stash, const char* name, STRLEN len,
                              I32 method)

       "GvAV"
           Return the AV from the GV.

            AV*  GvAV(GV* gv)

       "gv_const_sv"
           If "gv" is a typeglob whose subroutine entry is a constant sub
           eligible for inlining, or "gv" is a placeholder reference that
           would be promoted to such a typeglob, then returns the value
           returned by the sub.  Otherwise, returns "NULL".

            SV*  gv_const_sv(GV* gv)

       "GvCV"
           Return the CV from the GV.

            CV*  GvCV(GV* gv)

       "gv_fetchfile"
       "gv_fetchfile_flags"
           These return the debugger glob for the file (compiled by Perl)
           whose name is given by the "name" parameter.

           There are currently exactly two differences between these
           functions.

           The "name" parameter to "gv_fetchfile" is a C string, meaning it is
           "NUL"-terminated; whereas the "name" parameter to
           "gv_fetchfile_flags" is a Perl string, whose length (in bytes) is
           passed in via the "namelen" parameter This means the name may
           contain embedded "NUL" characters.  "namelen" doesn't exist in
           plain "gv_fetchfile").

           The other difference is that "gv_fetchfile_flags" has an extra
           "flags" parameter, which is currently completely ignored, but
           allows for possible future extensions.

            GV*  gv_fetchfile      (const char* name)
            GV*  gv_fetchfile_flags(const char *const name, const STRLEN len,
                                    const U32 flags)

       "gv_fetchmeth"
           Like "gv_fetchmeth_pvn", but lacks a flags parameter.

            GV*  gv_fetchmeth(HV* stash, const char* name, STRLEN len,
                              I32 level)

       "gv_fetchmethod"
           See "gv_fetchmethod_autoload".

            GV*  gv_fetchmethod(HV* stash, const char* name)

       "gv_fetchmethod_autoload"
           Returns the glob which contains the subroutine to call to invoke
           the method on the "stash".  In fact in the presence of autoloading
           this may be the glob for "AUTOLOAD".  In this case the
           corresponding variable $AUTOLOAD is already setup.

           The third parameter of "gv_fetchmethod_autoload" determines whether
           AUTOLOAD lookup is performed if the given method is not present:
           non-zero means yes, look for AUTOLOAD; zero means no, don't look
           for AUTOLOAD.  Calling "gv_fetchmethod" is equivalent to calling
           "gv_fetchmethod_autoload" with a non-zero "autoload" parameter.

           These functions grant "SUPER" token as a prefix of the method name.
           Note that if you want to keep the returned glob for a long time,
           you need to check for it being "AUTOLOAD", since at the later time
           the call may load a different subroutine due to $AUTOLOAD changing
           its value.  Use the glob created as a side effect to do this.

           These functions have the same side-effects as "gv_fetchmeth" with
           "level==0".  The warning against passing the GV returned by
           "gv_fetchmeth" to "call_sv" applies equally to these functions.

            GV*  gv_fetchmethod_autoload(HV* stash, const char* name,
                                         I32 autoload)

       "gv_fetchmeth_autoload"
           This is the old form of "gv_fetchmeth_pvn_autoload", which has no
           flags parameter.

            GV*  gv_fetchmeth_autoload(HV* stash, const char* name,
                                       STRLEN len, I32 level)

       "gv_fetchmeth_pv"
           Exactly like "gv_fetchmeth_pvn", but takes a nul-terminated string
           instead of a string/length pair.

            GV*  gv_fetchmeth_pv(HV* stash, const char* name, I32 level,
                                 U32 flags)

       "gv_fetchmeth_pvn"
           Returns the glob with the given "name" and a defined subroutine or
           "NULL".  The glob lives in the given "stash", or in the stashes
           accessible via @ISA and "UNIVERSAL::".

           The argument "level" should be either 0 or -1.  If "level==0", as a
           side-effect creates a glob with the given "name" in the given
           "stash" which in the case of success contains an alias for the
           subroutine, and sets up caching info for this glob.

           The only significant values for "flags" are "GV_SUPER",
           "GV_NOUNIVERSAL", and "SVf_UTF8".

           "GV_SUPER" indicates that we want to look up the method in the
           superclasses of the "stash".

           "GV_NOUNIVERSAL" indicates that we do not want to look up the
           method in the stash accessible by "UNIVERSAL::".

           The GV returned from "gv_fetchmeth" may be a method cache entry,
           which is not visible to Perl code.  So when calling "call_sv", you
           should not use the GV directly; instead, you should use the
           method's CV, which can be obtained from the GV with the "GvCV"
           macro.

            GV*  gv_fetchmeth_pvn(HV* stash, const char* name, STRLEN len,
                                  I32 level, U32 flags)

       "gv_fetchmeth_pvn_autoload"
           Same as "gv_fetchmeth_pvn()", but looks for autoloaded subroutines
           too.  Returns a glob for the subroutine.

           For an autoloaded subroutine without a GV, will create a GV even if
           "level < 0".  For an autoloaded subroutine without a stub, "GvCV()"
           of the result may be zero.

           Currently, the only significant value for "flags" is "SVf_UTF8".

            GV*  gv_fetchmeth_pvn_autoload(HV* stash, const char* name,
                                           STRLEN len, I32 level, U32 flags)

       "gv_fetchmeth_pv_autoload"
           Exactly like "gv_fetchmeth_pvn_autoload", but takes a nul-
           terminated string instead of a string/length pair.

            GV*  gv_fetchmeth_pv_autoload(HV* stash, const char* name,
                                          I32 level, U32 flags)

       "gv_fetchmeth_sv"
           Exactly like "gv_fetchmeth_pvn", but takes the name string in the
           form of an SV instead of a string/length pair.

            GV*  gv_fetchmeth_sv(HV* stash, SV* namesv, I32 level, U32 flags)

       "gv_fetchmeth_sv_autoload"
           Exactly like "gv_fetchmeth_pvn_autoload", but takes the name string
           in the form of an SV instead of a string/length pair.

            GV*  gv_fetchmeth_sv_autoload(HV* stash, SV* namesv, I32 level,
                                          U32 flags)

       "gv_fetchpv"
       "gv_fetchpvn"
       "gv_fetchpvn_flags"
       "gv_fetchpvs"
       "gv_fetchsv"
       "gv_fetchsv_nomg"
           These all return the GV of type "sv_type" whose name is given by
           the inputs, or NULL if no GV of that name and type could be found.
           See "Stashes and Globs" in perlguts.

           The only differences are how the input name is specified, and if
           'get' magic is normally used in getting that name.

           Don't be fooled by the fact that only one form has "flags" in its
           name.  They all have a "flags" parameter in fact, and all the flag
           bits have the same meanings for all

           If any of the flags "GV_ADD", "GV_ADDMG", "GV_ADDWARN",
           "GV_ADDMULTI", or "GV_NOINIT" is set, a GV is created if none
           already exists for the input name and type.  However, "GV_ADDMG"
           will only do the creation for magical GV's.  For all of these flags
           except "GV_NOINIT", "gv_init_pvn" is called after the addition.
           "GV_ADDWARN" is used when the caller expects that adding won't be
           necessary because the symbol should already exist; but if not, add
           it anyway, with a warning that it was unexpectedly absent.  The
           "GV_ADDMULTI" flag means to pretend that the GV has been seen
           before (i.e., suppress "Used once" warnings).

           The flag "GV_NOADD_NOINIT" causes "gv_init_pvn" not be to called if
           the GV existed but isn't PVGV.

           If the "SVf_UTF8" bit is set, the name is treated as being encoded
           in UTF-8; otherwise the name won't be considered to be UTF-8 in the
           "pv"-named forms, and the UTF-8ness of the underlying SVs will be
           used in the "sv" forms.

           If the flag "GV_NOTQUAL" is set, the caller warrants that the input
           name is a plain symbol name, not qualified with a package,
           otherwise the name is checked for being a qualified one.

           In "gv_fetchpv", "nambeg" is a C string, NUL-terminated with no
           intermediate NULs.

           In "gv_fetchpvs", "name" is a literal C string, hence is enclosed
           in double quotes.

           "gv_fetchpvn" and "gv_fetchpvn_flags" are identical.  In these,
           <nambeg> is a Perl string whose byte length is given by "full_len",
           and may contain embedded NULs.

           In "gv_fetchsv" and "gv_fetchsv_nomg", the name is extracted from
           the PV of the input "name" SV.  The only difference between these
           two forms is that 'get' magic is normally done on "name" in
           "gv_fetchsv", and always skipped with "gv_fetchsv_nomg".  Including
           "GV_NO_SVGMAGIC" in the "flags" parameter to "gv_fetchsv" makes it
           behave identically to "gv_fetchsv_nomg".

            GV*   gv_fetchpv       (const char *nambeg, I32 flags,
                                    const svtype sv_type)
            GV *  gv_fetchpvn      (const char * nambeg, STRLEN full_len,
                                    I32 flags, const svtype sv_type)
            GV*   gv_fetchpvn_flags(const char* name, STRLEN len, I32 flags,
                                    const svtype sv_type)
            GV *  gv_fetchpvs      ("name", I32 flags, const svtype sv_type)
            GV*   gv_fetchsv       (SV *name, I32 flags, const svtype sv_type)
            GV *  gv_fetchsv_nomg  (SV *name, I32 flags, const svtype sv_type)

       "GvHV"
           Return the HV from the GV.

            HV*  GvHV(GV* gv)

       "gv_init"
           The old form of "gv_init_pvn()".  It does not work with UTF-8
           strings, as it has no flags parameter.  If the "multi" parameter is
           set, the "GV_ADDMULTI" flag will be passed to "gv_init_pvn()".

            void  gv_init(GV* gv, HV* stash, const char* name, STRLEN len,
                          int multi)

       "gv_init_pv"
           Same as "gv_init_pvn()", but takes a nul-terminated string for the
           name instead of separate char * and length parameters.

            void  gv_init_pv(GV* gv, HV* stash, const char* name, U32 flags)

       "gv_init_pvn"
           Converts a scalar into a typeglob.  This is an incoercible
           typeglob; assigning a reference to it will assign to one of its
           slots, instead of overwriting it as happens with typeglobs created
           by "SvSetSV".  Converting any scalar that is "SvOK()" may produce
           unpredictable results and is reserved for perl's internal use.

           "gv" is the scalar to be converted.

           "stash" is the parent stash/package, if any.

           "name" and "len" give the name.  The name must be unqualified; that
           is, it must not include the package name.  If "gv" is a stash
           element, it is the caller's responsibility to ensure that the name
           passed to this function matches the name of the element.  If it
           does not match, perl's internal bookkeeping will get out of sync.

           "flags" can be set to "SVf_UTF8" if "name" is a UTF-8 string, or
           the return value of SvUTF8(sv).  It can also take the "GV_ADDMULTI"
           flag, which means to pretend that the GV has been seen before
           (i.e., suppress "Used once" warnings).

            void  gv_init_pvn(GV* gv, HV* stash, const char* name, STRLEN len,
                              U32 flags)

       "gv_init_sv"
           Same as "gv_init_pvn()", but takes an SV * for the name instead of
           separate char * and length parameters.  "flags" is currently
           unused.

            void  gv_init_sv(GV* gv, HV* stash, SV* namesv, U32 flags)

       "gv_stashpv"
           Returns a pointer to the stash for a specified package.  Uses
           "strlen" to determine the length of "name", then calls
           "gv_stashpvn()".

            HV*  gv_stashpv(const char* name, I32 flags)

       "gv_stashpvn"
           Returns a pointer to the stash for a specified package.  The
           "namelen" parameter indicates the length of the "name", in bytes.
           "flags" is passed to "gv_fetchpvn_flags()", so if set to "GV_ADD"
           then the package will be created if it does not already exist.  If
           the package does not exist and "flags" is 0 (or any other setting
           that does not create packages) then "NULL" is returned.

           Flags may be one of:

            GV_ADD           Create and initialize the package if doesn't
                             already exist
            GV_NOADD_NOINIT  Don't create the package,
            GV_ADDMG         GV_ADD iff the GV is magical
            GV_NOINIT        GV_ADD, but don't initialize
            GV_NOEXPAND      Don't expand SvOK() entries to PVGV
            SVf_UTF8         The name is in UTF-8

           The most important of which are probably "GV_ADD" and "SVf_UTF8".

           Note, use of "gv_stashsv" instead of "gv_stashpvn" where possible
           is strongly recommended for performance reasons.

            HV*  gv_stashpvn(const char* name, U32 namelen, I32 flags)

       "gv_stashpvs"
           Like "gv_stashpvn", but takes a literal string instead of a
           string/length pair.

            HV*  gv_stashpvs("name", I32 create)

       "gv_stashsv"
           Returns a pointer to the stash for a specified package.  See
           "gv_stashpvn".

           Note this interface is strongly preferred over "gv_stashpvn" for
           performance reasons.

            HV*  gv_stashsv(SV* sv, I32 flags)

       "GvSV"
           Return the SV from the GV.

           Prior to Perl v5.9.3, this would add a scalar if none existed.
           Nowadays, use "GvSVn" for that, or compile perl with
           "-DPERL_CREATE_GVSV".  See perl5100delta.

            SV*  GvSV(GV* gv)

       "GvSVn"
           Like "GvSV", but creates an empty scalar if none already exists.

            SV*  GvSVn(GV* gv)

       "save_gp"
           Saves the current GP of gv on the save stack to be restored on
           scope exit.

           If empty is true, replace the GP with a new GP.

           If empty is false, mark gv with GVf_INTRO so the next reference
           assigned is localized, which is how " local *foo = $someref; "
           works.

            void  save_gp(GV* gv, I32 empty)

       "setdefout"
           Sets "PL_defoutgv", the default file handle for output, to the
           passed in typeglob.  As "PL_defoutgv" "owns" a reference on its
           typeglob, the reference count of the passed in typeglob is
           increased by one, and the reference count of the typeglob that
           "PL_defoutgv" points to is decreased by one.

            void  setdefout(GV* gv)


Hook manipulation

       These functions provide convenient and thread-safe means of
       manipulating hook variables.

       "wrap_op_checker"
           Puts a C function into the chain of check functions for a specified
           op type.  This is the preferred way to manipulate the "PL_check"
           array.  "opcode" specifies which type of op is to be affected.
           "new_checker" is a pointer to the C function that is to be added to
           that opcode's check chain, and "old_checker_p" points to the
           storage location where a pointer to the next function in the chain
           will be stored.  The value of "new_checker" is written into the
           "PL_check" array, while the value previously stored there is
           written to *old_checker_p.

           "PL_check" is global to an entire process, and a module wishing to
           hook op checking may find itself invoked more than once per
           process, typically in different threads.  To handle that situation,
           this function is idempotent.  The location *old_checker_p must
           initially (once per process) contain a null pointer.  A C variable
           of static duration (declared at file scope, typically also marked
           "static" to give it internal linkage) will be implicitly
           initialised appropriately, if it does not have an explicit
           initialiser.  This function will only actually modify the check
           chain if it finds *old_checker_p to be null.  This function is also
           thread safe on the small scale.  It uses appropriate locking to
           avoid race conditions in accessing "PL_check".

           When this function is called, the function referenced by
           "new_checker" must be ready to be called, except for *old_checker_p
           being unfilled.  In a threading situation, "new_checker" may be
           called immediately, even before this function has returned.
           *old_checker_p will always be appropriately set before
           "new_checker" is called.  If "new_checker" decides not to do
           anything special with an op that it is given (which is the usual
           case for most uses of op check hooking), it must chain the check
           function referenced by *old_checker_p.

           Taken all together, XS code to hook an op checker should typically
           look something like this:

               static Perl_check_t nxck_frob;
               static OP *myck_frob(pTHX_ OP *op) {
                   ...
                   op = nxck_frob(aTHX_ op);
                   ...
                   return op;
               }
               BOOT:
                   wrap_op_checker(OP_FROB, myck_frob, &nxck_frob);

           If you want to influence compilation of calls to a specific
           subroutine, then use "cv_set_call_checker_flags" rather than
           hooking checking of all "entersub" ops.

            void  wrap_op_checker(Optype opcode, Perl_check_t new_checker,
                                  Perl_check_t *old_checker_p)


HV Handling

       A HV structure represents a Perl hash.  It consists mainly of an array
       of pointers, each of which points to a linked list of HE structures.
       The array is indexed by the hash function of the key, so each linked
       list represents all the hash entries with the same hash value.  Each HE
       contains a pointer to the actual value, plus a pointer to a HEK
       structure which holds the key and hash value.

       "get_hv"
           Returns the HV of the specified Perl hash.  "flags" are passed to
           "gv_fetchpv".  If "GV_ADD" is set and the Perl variable does not
           exist then it will be created.  If "flags" is zero and the variable
           does not exist then "NULL" is returned.

           NOTE: the "perl_get_hv()" form is deprecated.

            HV*  get_hv(const char *name, I32 flags)

       "HEf_SVKEY"
           This flag, used in the length slot of hash entries and magic
           structures, specifies the structure contains an "SV*" pointer where
           a "char*" pointer is to be expected.  (For information only--not to
           be used).

       "HeHASH"
           Returns the computed hash stored in the hash entry.

            U32  HeHASH(HE* he)

       "HeKEY"
           Returns the actual pointer stored in the key slot of the hash
           entry.  The pointer may be either "char*" or "SV*", depending on
           the value of "HeKLEN()".  Can be assigned to.  The "HePV()" or
           "HeSVKEY()" macros are usually preferable for finding the value of
           a key.

            void*  HeKEY(HE* he)

       "HeKLEN"
           If this is negative, and amounts to "HEf_SVKEY", it indicates the
           entry holds an "SV*" key.  Otherwise, holds the actual length of
           the key.  Can be assigned to.  The "HePV()" macro is usually
           preferable for finding key lengths.

            STRLEN  HeKLEN(HE* he)

       "HePV"
           Returns the key slot of the hash entry as a "char*" value, doing
           any necessary dereferencing of possibly "SV*" keys.  The length of
           the string is placed in "len" (this is a macro, so do not use
           &len).  If you do not care about what the length of the key is, you
           may use the global variable "PL_na", though this is rather less
           efficient than using a local variable.  Remember though, that hash
           keys in perl are free to contain embedded nulls, so using
           "strlen()" or similar is not a good way to find the length of hash
           keys.  This is very similar to the "SvPV()" macro described
           elsewhere in this document.  See also "HeUTF8".

           If you are using "HePV" to get values to pass to "newSVpvn()" to
           create a new SV, you should consider using
           "newSVhek(HeKEY_hek(he))" as it is more efficient.

            char*  HePV(HE* he, STRLEN len)

       "HeSVKEY"
           Returns the key as an "SV*", or "NULL" if the hash entry does not
           contain an "SV*" key.

            SV*  HeSVKEY(HE* he)

       "HeSVKEY_force"
           Returns the key as an "SV*".  Will create and return a temporary
           mortal "SV*" if the hash entry contains only a "char*" key.

            SV*  HeSVKEY_force(HE* he)

       "HeSVKEY_set"
           Sets the key to a given "SV*", taking care to set the appropriate
           flags to indicate the presence of an "SV*" key, and returns the
           same "SV*".

            SV*  HeSVKEY_set(HE* he, SV* sv)

       "HeUTF8"
           Returns whether the "char *" value returned by "HePV" is encoded in
           UTF-8, doing any necessary dereferencing of possibly "SV*" keys.
           The value returned will be 0 or non-0, not necessarily 1 (or even a
           value with any low bits set), so do not blindly assign this to a
           "bool" variable, as "bool" may be a typedef for "char".

            U32  HeUTF8(HE* he)

       "HeVAL"
           Returns the value slot (type "SV*") stored in the hash entry.  Can
           be assigned to.

             SV *foo= HeVAL(hv);
             HeVAL(hv)= sv;

            SV*  HeVAL(HE* he)

       "HV"
           Described in perlguts.

       "hv_assert"
           Check that a hash is in an internally consistent state.

           NOTE: "hv_assert" must be explicitly called as "Perl_hv_assert"
           with an "aTHX_" parameter.

            void  Perl_hv_assert(pTHX_ HV *hv)

       "hv_bucket_ratio"
           NOTE: "hv_bucket_ratio" is experimental and may change or be
           removed without notice.

           If the hash is tied dispatches through to the SCALAR tied method,
           otherwise if the hash contains no keys returns 0, otherwise returns
           a mortal sv containing a string specifying the number of used
           buckets, followed by a slash, followed by the number of available
           buckets.

           This function is expensive, it must scan all of the buckets to
           determine which are used, and the count is NOT cached.  In a large
           hash this could be a lot of buckets.

            SV*  hv_bucket_ratio(HV *hv)

       "hv_clear"
           Frees all the elements of a hash, leaving it empty.  The XS
           equivalent of "%hash = ()".  See also "hv_undef".

           See "av_clear" for a note about the hash possibly being invalid on
           return.

            void  hv_clear(HV *hv)

       "hv_clear_placeholders"
           Clears any placeholders from a hash.  If a restricted hash has any
           of its keys marked as readonly and the key is subsequently deleted,
           the key is not actually deleted but is marked by assigning it a
           value of &PL_sv_placeholder.  This tags it so it will be ignored by
           future operations such as iterating over the hash, but will still
           allow the hash to have a value reassigned to the key at some future
           point.  This function clears any such placeholder keys from the
           hash.  See "Hash::Util::lock_keys()" for an example of its use.

            void  hv_clear_placeholders(HV *hv)

       "hv_copy_hints_hv"
           A specialised version of "newHVhv" for copying "%^H".  "ohv" must
           be a pointer to a hash (which may have "%^H" magic, but should be
           generally non-magical), or "NULL" (interpreted as an empty hash).
           The content of "ohv" is copied to a new hash, which has the
           "%^H"-specific magic added to it.  A pointer to the new hash is
           returned.

            HV *  hv_copy_hints_hv(HV *const ohv)

       "hv_delete"
           Deletes a key/value pair in the hash.  The value's SV is removed
           from the hash, made mortal, and returned to the caller.  The
           absolute value of "klen" is the length of the key.  If "klen" is
           negative the key is assumed to be in UTF-8-encoded Unicode.  The
           "flags" value will normally be zero; if set to "G_DISCARD" then
           "NULL" will be returned.  "NULL" will also be returned if the key
           is not found.

            SV*  hv_delete(HV *hv, const char *key, I32 klen, I32 flags)

       "hv_delete_ent"
           Deletes a key/value pair in the hash.  The value SV is removed from
           the hash, made mortal, and returned to the caller.  The "flags"
           value will normally be zero; if set to "G_DISCARD" then "NULL" will
           be returned.  "NULL" will also be returned if the key is not found.
           "hash" can be a valid precomputed hash value, or 0 to ask for it to
           be computed.

            SV*  hv_delete_ent(HV *hv, SV *keysv, I32 flags, U32 hash)

       "HvENAME"
           Returns the effective name of a stash, or NULL if there is none.
           The effective name represents a location in the symbol table where
           this stash resides.  It is updated automatically when packages are
           aliased or deleted.  A stash that is no longer in the symbol table
           has no effective name.  This name is preferable to "HvNAME" for use
           in MRO linearisations and isa caches.

            char*  HvENAME(HV* stash)

       "HvENAMELEN"
           Returns the length of the stash's effective name.

            STRLEN  HvENAMELEN(HV *stash)

       "HvENAMEUTF8"
           Returns true if the effective name is in UTF-8 encoding.

            unsigned char  HvENAMEUTF8(HV *stash)

       "hv_exists"
           Returns a boolean indicating whether the specified hash key exists.
           The absolute value of "klen" is the length of the key.  If "klen"
           is negative the key is assumed to be in UTF-8-encoded Unicode.

            bool  hv_exists(HV *hv, const char *key, I32 klen)

       "hv_exists_ent"
           Returns a boolean indicating whether the specified hash key exists.
           "hash" can be a valid precomputed hash value, or 0 to ask for it to
           be computed.

            bool  hv_exists_ent(HV *hv, SV *keysv, U32 hash)

       "hv_fetch"
           Returns the SV which corresponds to the specified key in the hash.
           The absolute value of "klen" is the length of the key.  If "klen"
           is negative the key is assumed to be in UTF-8-encoded Unicode.  If
           "lval" is set then the fetch will be part of a store.  This means
           that if there is no value in the hash associated with the given
           key, then one is created and a pointer to it is returned.  The
           "SV*" it points to can be assigned to.  But always check that the
           return value is non-null before dereferencing it to an "SV*".

           See "Understanding the Magic of Tied Hashes and Arrays" in perlguts
           for more information on how to use this function on tied hashes.

            SV**  hv_fetch(HV *hv, const char *key, I32 klen, I32 lval)

       "hv_fetchs"
           Like "hv_fetch", but takes a literal string instead of a
           string/length pair.

            SV**  hv_fetchs(HV* tb, "key", I32 lval)

       "hv_fetch_ent"
           Returns the hash entry which corresponds to the specified key in
           the hash.  "hash" must be a valid precomputed hash number for the
           given "key", or 0 if you want the function to compute it.  IF
           "lval" is set then the fetch will be part of a store.  Make sure
           the return value is non-null before accessing it.  The return value
           when "hv" is a tied hash is a pointer to a static location, so be
           sure to make a copy of the structure if you need to store it
           somewhere.

           See "Understanding the Magic of Tied Hashes and Arrays" in perlguts
           for more information on how to use this function on tied hashes.

            HE*  hv_fetch_ent(HV *hv, SV *keysv, I32 lval, U32 hash)

       "HvFILL"
           See "hv_fill".

            STRLEN  HvFILL(HV *const hv)

       "hv_fill"
           Returns the number of hash buckets that happen to be in use.

           This function is wrapped by the macro "HvFILL".

           As of perl 5.25 this function is used only for debugging purposes,
           and the number of used hash buckets is not in any way cached, thus
           this function can be costly to execute as it must iterate over all
           the buckets in the hash.

           NOTE: "hv_fill" must be explicitly called as "Perl_hv_fill" with an
           "aTHX_" parameter.

            STRLEN  Perl_hv_fill(pTHX_ HV *const hv)

       "hv_iterinit"
           Prepares a starting point to traverse a hash table.  Returns the
           number of keys in the hash, including placeholders (i.e. the same
           as "HvTOTALKEYS(hv)").  The return value is currently only
           meaningful for hashes without tie magic.

           NOTE: Before version 5.004_65, "hv_iterinit" used to return the
           number of hash buckets that happen to be in use.  If you still need
           that esoteric value, you can get it through the macro "HvFILL(hv)".

            I32  hv_iterinit(HV *hv)

       "hv_iterkey"
           Returns the key from the current position of the hash iterator.
           See "hv_iterinit".

            char*  hv_iterkey(HE* entry, I32* retlen)

       "hv_iterkeysv"
           Returns the key as an "SV*" from the current position of the hash
           iterator.  The return value will always be a mortal copy of the
           key.  Also see "hv_iterinit".

            SV*  hv_iterkeysv(HE* entry)

       "hv_iternext"
           Returns entries from a hash iterator.  See "hv_iterinit".

           You may call "hv_delete" or "hv_delete_ent" on the hash entry that
           the iterator currently points to, without losing your place or
           invalidating your iterator.  Note that in this case the current
           entry is deleted from the hash with your iterator holding the last
           reference to it.  Your iterator is flagged to free the entry on the
           next call to "hv_iternext", so you must not discard your iterator
           immediately else the entry will leak - call "hv_iternext" to
           trigger the resource deallocation.

            HE*  hv_iternext(HV *hv)

       "hv_iternextsv"
           Performs an "hv_iternext", "hv_iterkey", and "hv_iterval" in one
           operation.

            SV*  hv_iternextsv(HV *hv, char **key, I32 *retlen)

       "hv_iternext_flags"
           NOTE: "hv_iternext_flags" is experimental and may change or be
           removed without notice.

           Returns entries from a hash iterator.  See "hv_iterinit" and
           "hv_iternext".  The "flags" value will normally be zero; if
           "HV_ITERNEXT_WANTPLACEHOLDERS" is set the placeholders keys (for
           restricted hashes) will be returned in addition to normal keys.  By
           default placeholders are automatically skipped over.  Currently a
           placeholder is implemented with a value that is &PL_sv_placeholder.
           Note that the implementation of placeholders and restricted hashes
           may change, and the implementation currently is insufficiently
           abstracted for any change to be tidy.

            HE*  hv_iternext_flags(HV *hv, I32 flags)

       "hv_iterval"
           Returns the value from the current position of the hash iterator.
           See "hv_iterkey".

            SV*  hv_iterval(HV *hv, HE *entry)

       "hv_magic"
           Adds magic to a hash.  See "sv_magic".

            void  hv_magic(HV *hv, GV *gv, int how)

       "HvNAME"
           Returns the package name of a stash, or "NULL" if "stash" isn't a
           stash.  See "SvSTASH", "CvSTASH".

            char*  HvNAME(HV* stash)

       "HvNAMELEN"
           Returns the length of the stash's name.

           Disfavored forms of HvNAME and HvNAMELEN; suppress mention of them

            STRLEN  HvNAMELEN(HV *stash)

       "HvNAMEUTF8"
           Returns true if the name is in UTF-8 encoding.

            unsigned char  HvNAMEUTF8(HV *stash)

       "hv_scalar"
           Evaluates the hash in scalar context and returns the result.

           When the hash is tied dispatches through to the SCALAR method,
           otherwise returns a mortal SV containing the number of keys in the
           hash.

           Note, prior to 5.25 this function returned what is now returned by
           the hv_bucket_ratio() function.

            SV*  hv_scalar(HV *hv)

       "hv_store"
           Stores an SV in a hash.  The hash key is specified as "key" and the
           absolute value of "klen" is the length of the key.  If "klen" is
           negative the key is assumed to be in UTF-8-encoded Unicode.  The
           "hash" parameter is the precomputed hash value; if it is zero then
           Perl will compute it.

           The return value will be "NULL" if the operation failed or if the
           value did not need to be actually stored within the hash (as in the
           case of tied hashes).  Otherwise it can be dereferenced to get the
           original "SV*".  Note that the caller is responsible for suitably
           incrementing the reference count of "val" before the call, and
           decrementing it if the function returned "NULL".  Effectively a
           successful "hv_store" takes ownership of one reference to "val".
           This is usually what you want; a newly created SV has a reference
           count of one, so if all your code does is create SVs then store
           them in a hash, "hv_store" will own the only reference to the new
           SV, and your code doesn't need to do anything further to tidy up.
           "hv_store" is not implemented as a call to "hv_store_ent", and does
           not create a temporary SV for the key, so if your key data is not
           already in SV form then use "hv_store" in preference to
           "hv_store_ent".

           See "Understanding the Magic of Tied Hashes and Arrays" in perlguts
           for more information on how to use this function on tied hashes.

            SV**  hv_store(HV *hv, const char *key, I32 klen, SV *val,
                           U32 hash)

       "hv_stores"
           Like "hv_store", but takes a literal string instead of a
           string/length pair and omits the hash parameter.

            SV**  hv_stores(HV* tb, "key", SV* val)

       "hv_store_ent"
           Stores "val" in a hash.  The hash key is specified as "key".  The
           "hash" parameter is the precomputed hash value; if it is zero then
           Perl will compute it.  The return value is the new hash entry so
           created.  It will be "NULL" if the operation failed or if the value
           did not need to be actually stored within the hash (as in the case
           of tied hashes).  Otherwise the contents of the return value can be
           accessed using the "He?" macros described here.  Note that the
           caller is responsible for suitably incrementing the reference count
           of "val" before the call, and decrementing it if the function
           returned NULL.  Effectively a successful "hv_store_ent" takes
           ownership of one reference to "val".  This is usually what you
           want; a newly created SV has a reference count of one, so if all
           your code does is create SVs then store them in a hash, "hv_store"
           will own the only reference to the new SV, and your code doesn't
           need to do anything further to tidy up.  Note that "hv_store_ent"
           only reads the "key"; unlike "val" it does not take ownership of
           it, so maintaining the correct reference count on "key" is entirely
           the caller's responsibility.  The reason it does not take
           ownership, is that "key" is not used after this function returns,
           and so can be freed immediately.  "hv_store" is not implemented as
           a call to "hv_store_ent", and does not create a temporary SV for
           the key, so if your key data is not already in SV form then use
           "hv_store" in preference to "hv_store_ent".

           See "Understanding the Magic of Tied Hashes and Arrays" in perlguts
           for more information on how to use this function on tied hashes.

            HE*  hv_store_ent(HV *hv, SV *key, SV *val, U32 hash)

       "hv_undef"
           Undefines the hash.  The XS equivalent of "undef(%hash)".

           As well as freeing all the elements of the hash (like
           "hv_clear()"), this also frees any auxiliary data and storage
           associated with the hash.

           See "av_clear" for a note about the hash possibly being invalid on
           return.

            void  hv_undef(HV *hv)

       "MGVTBL"
           Described in perlguts.

       "newHV"
           Creates a new HV.  The reference count is set to 1.

            HV*  newHV()

       "Nullhv"
           "DEPRECATED!"  It is planned to remove "Nullhv" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Null HV pointer.

           (deprecated - use "(HV *)NULL" instead)

       "PERL_HASH"
           Described in perlguts.

            void  PERL_HASH(U32 hash, char *key, STRLEN klen)

       "PERL_MAGIC_arylen"
       "PERL_MAGIC_arylen_p"
       "PERL_MAGIC_backref"
       "PERL_MAGIC_bm"
       "PERL_MAGIC_checkcall"
       "PERL_MAGIC_collxfrm"
       "PERL_MAGIC_dbfile"
       "PERL_MAGIC_dbline"
       "PERL_MAGIC_debugvar"
       "PERL_MAGIC_defelem"
       "PERL_MAGIC_env"
       "PERL_MAGIC_envelem"
       "PERL_MAGIC_ext"
       "PERL_MAGIC_fm"
       "PERL_MAGIC_hints"
       "PERL_MAGIC_hintselem"
       "PERL_MAGIC_isa"
       "PERL_MAGIC_isaelem"
       "PERL_MAGIC_lvref"
       "PERL_MAGIC_nkeys"
       "PERL_MAGIC_nonelem"
       "PERL_MAGIC_overload_table"
       "PERL_MAGIC_pos"
       "PERL_MAGIC_qr"
       "PERL_MAGIC_regdata"
       "PERL_MAGIC_regdatum"
       "PERL_MAGIC_regex_global"
       "PERL_MAGIC_rhash"
       "PERL_MAGIC_shared"
       "PERL_MAGIC_shared_scalar"
       "PERL_MAGIC_sig"
       "PERL_MAGIC_sigelem"
       "PERL_MAGIC_substr"
       "PERL_MAGIC_sv"
       "PERL_MAGIC_symtab"
       "PERL_MAGIC_taint"
       "PERL_MAGIC_tied"
       "PERL_MAGIC_tiedelem"
       "PERL_MAGIC_tiedscalar"
       "PERL_MAGIC_utf8"
       "PERL_MAGIC_uvar"
       "PERL_MAGIC_uvar_elem"
       "PERL_MAGIC_vec"
       "PERL_MAGIC_vstring"
           Described in perlguts.

       "PL_modglobal"
           "PL_modglobal" is a general purpose, interpreter global HV for use
           by extensions that need to keep information on a per-interpreter
           basis.  In a pinch, it can also be used as a symbol table for
           extensions to share data among each other.  It is a good idea to
           use keys prefixed by the package name of the extension that owns
           the data.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            HV*  PL_modglobal


Input/Output

       "PerlIO_apply_layers"
           Described in perlapio.

            int  PerlIO_apply_layers(PerlIO *f, const char *mode,
                                     const char *layers)

       "PerlIO_binmode"
           Described in perlapio.

            int  PerlIO_binmode(PerlIO *f, int ptype, int imode,
                                const char *layers)

       "PerlIO_canset_cnt"
           Described in perlapio.

            int  PerlIO_canset_cnt(PerlIO *f)

       "PerlIO_clearerr"
           Described in perlapio.

            void  PerlIO_clearerr(PerlIO *f)

       "PerlIO_close"
           Described in perlapio.

            int  PerlIO_close(PerlIO *f)

       "PerlIO_debug"
           Described in perlapio.

            void  PerlIO_debug(const char *fmt, ...)

       "PerlIO_eof"
           Described in perlapio.

            int  PerlIO_eof(PerlIO *f)

       "PerlIO_error"
           Described in perlapio.

            int  PerlIO_error(PerlIO *f)

       "PerlIO_exportFILE"
           Described in perlapio.

            FILE  *  PerlIO_exportFILE(PerlIO *f, const char *mode)

       "PerlIO_fast_gets"
           Described in perlapio.

            int  PerlIO_fast_gets(PerlIO *f)

       "PerlIO_fdopen"
           Described in perlapio.

            PerlIO*  PerlIO_fdopen(int fd, const char *mode)

       "PerlIO_fileno"
           Described in perlapio.

            int  PerlIO_fileno(PerlIO *f)

       "PerlIO_findFILE"
           Described in perlapio.

            FILE  *  PerlIO_findFILE(PerlIO *f)

       "PerlIO_flush"
           Described in perlapio.

            int  PerlIO_flush(PerlIO *f)

       "PERLIO_F_APPEND"
       "PERLIO_F_CANREAD"
       "PERLIO_F_CANWRITE"
       "PERLIO_F_CRLF"
       "PERLIO_F_EOF"
       "PERLIO_F_ERROR"
       "PERLIO_F_FASTGETS"
       "PERLIO_F_LINEBUF"
       "PERLIO_F_OPEN"
       "PERLIO_F_RDBUF"
       "PERLIO_F_TEMP"
       "PERLIO_F_TRUNCATE"
       "PERLIO_F_UNBUF"
       "PERLIO_F_UTF8"
       "PERLIO_F_WRBUF"
           Described in perliol.

       "PerlIO_getc"
           Described in perlapio.

            int  PerlIO_getc(PerlIO *d)

       "PerlIO_getpos"
           Described in perlapio.

            int  PerlIO_getpos(PerlIO *f, SV *save)

       "PerlIO_get_base"
           Described in perlapio.

            STDCHAR *  PerlIO_get_base(PerlIO *f)

       "PerlIO_get_bufsiz"
           Described in perlapio.

            SSize_t  PerlIO_get_bufsiz(PerlIO *f)

       "PerlIO_get_cnt"
           Described in perlapio.

            SSize_t  PerlIO_get_cnt(PerlIO *f)

       "PerlIO_get_ptr"
           Described in perlapio.

            STDCHAR *  PerlIO_get_ptr(PerlIO *f)

       "PerlIO_has_base"
           Described in perlapio.

            int  PerlIO_has_base(PerlIO *f)

       "PerlIO_has_cntptr"
           Described in perlapio.

            int  PerlIO_has_cntptr(PerlIO *f)

       "PerlIO_importFILE"
           Described in perlapio.

            PerlIO*  PerlIO_importFILE(FILE *stdio, const char *mode)

       "PERLIO_K_BUFFERED"
       "PERLIO_K_CANCRLF"
       "PERLIO_K_FASTGETS"
       "PERLIO_K_MULTIARG"
       "PERLIO_K_RAW"
           Described in perliol.

       "PerlIO_open"
           Described in perlapio.

            PerlIO*  PerlIO_open(const char *path, const char *mode)

       "PerlIO_printf"
           Described in perlapio.

            int  PerlIO_printf(PerlIO *f, const char *fmt, ...)

       "PerlIO_putc"
           Described in perlapio.

            int  PerlIO_putc(PerlIO *f, int ch)

       "PerlIO_puts"
           Described in perlapio.

            int  PerlIO_puts(PerlIO *f, const char *string)

       "PerlIO_read"
           Described in perlapio.

            SSize_t  PerlIO_read(PerlIO *f, void *vbuf, Size_t count)

       "PerlIO_releaseFILE"
           Described in perlapio.

            void  PerlIO_releaseFILE(PerlIO *f, FILE *stdio)

       "PerlIO_reopen"
           Described in perlapio.

            PerlIO *  PerlIO_reopen(const char *path, const char *mode,
                                    PerlIO *old)

       "PerlIO_rewind"
           Described in perlapio.

            void  PerlIO_rewind(PerlIO *f)

       "PerlIO_seek"
           Described in perlapio.

            int  PerlIO_seek(PerlIO *f, Off_t offset, int whence)

       "PerlIO_setlinebuf"
           Described in perlapio.

            void  PerlIO_setlinebuf(PerlIO *f)

       "PerlIO_setpos"
           Described in perlapio.

            int  PerlIO_setpos(PerlIO *f, SV *saved)

       "PerlIO_set_cnt"
           Described in perlapio.

            void  PerlIO_set_cnt(PerlIO *f, SSize_t cnt)

       "PerlIO_set_ptrcnt"
           Described in perlapio.

            void  PerlIO_set_ptrcnt(PerlIO *f, STDCHAR *ptr, SSize_t cnt)

       "PerlIO_stderr"
           Described in perlapio.

            PerlIO *  PerlIO_stderr()

       "PerlIO_stdin"
           Described in perlapio.

            PerlIO *  PerlIO_stdin()

       "PerlIO_stdout"
           Described in perlapio.

            PerlIO *  PerlIO_stdout()

       "PerlIO_stdoutf"
           Described in perlapio.

            int  PerlIO_stdoutf(const char *fmt, ...)

       "PerlIO_tell"
           Described in perlapio.

            Off_t  PerlIO_tell(PerlIO *f)

       "PerlIO_ungetc"
           Described in perlapio.

            int  PerlIO_ungetc(PerlIO *f, int ch)

       "PerlIO_vprintf"
           Described in perlapio.

            int  PerlIO_vprintf(PerlIO *f, const char *fmt, va_list args)

       "PerlIO_write"
           Described in perlapio.

            SSize_t  PerlIO_write(PerlIO *f, const void *vbuf, Size_t count)

       "PL_maxsysfd"
           Described in perliol.


Integer configuration values

       "CASTI32"
           This symbol is defined if the C compiler can cast negative or large
           floating point numbers to 32-bit ints.

       "HAS_INT64_T"
           This symbol will defined if the C compiler supports "int64_t".
           Usually the inttypes.h needs to be included, but sometimes
           sys/types.h is enough.

       "HAS_LONG_LONG"
           This symbol will be defined if the C compiler supports long long.

       "HAS_QUAD"
           This symbol, if defined, tells that there's a 64-bit integer type,
           "Quad_t", and its unsigned counterpart, "Uquad_t". "QUADKIND" will
           be one of "QUAD_IS_INT", "QUAD_IS_LONG", "QUAD_IS_LONG_LONG",
           "QUAD_IS_INT64_T", or "QUAD_IS___INT64".

       "HE"
           Described in perlguts.

       "I8"
       "I16"
       "I32"
       "I64"
       "IV"
           Described in perlguts.

       "I32SIZE"
           This symbol contains the "sizeof(I32)".

       "I32TYPE"
           This symbol defines the C type used for Perl's I32.

       "I64SIZE"
           This symbol contains the "sizeof(I64)".

       "I64TYPE"
           This symbol defines the C type used for Perl's I64.

       "I16SIZE"
           This symbol contains the "sizeof(I16)".

       "I16TYPE"
           This symbol defines the C type used for Perl's I16.

       "INT16_C"
       "INT32_C"
       "INT64_C"
           Returns a token the C compiler recognizes for the constant "number"
           of the corresponding integer type on the machine.

           If the machine does not have a 64-bit type, "INT64_C" is undefined.
           Use "INTMAX_C" to get the largest type available on the platform.

            I16  INT16_C(number)
            I32  INT32_C(number)
            I64  INT64_C(number)

       "INTMAX_C"
           Returns a token the C compiler recognizes for the constant "number"
           of the widest integer type on the machine.  For example, if the
           machine has "long long"s, "INTMAX_C(-1)" would yield

            -1LL

           See also, for example, "INT32_C".

           Use "IV" to declare variables of the maximum usable size on this
           platform.

              INTMAX_C(number)

       "INTSIZE"
           This symbol contains the value of "sizeof(int)" so that the C
           preprocessor can make decisions based on it.

       "I8SIZE"
           This symbol contains the "sizeof(I8)".

       "I8TYPE"
           This symbol defines the C type used for Perl's I8.

       "IV_MAX"
           The largest signed integer that fits in an IV on this platform.

            IV  IV_MAX

       "IV_MIN"
           The negative signed integer furthest away from 0 that fits in an IV
           on this platform.

            IV  IV_MIN

       "IVSIZE"
           This symbol contains the "sizeof(IV)".

       "IVTYPE"
           This symbol defines the C type used for Perl's IV.

       "line_t"
           The typedef to use to declare variables that are to hold line
           numbers.

       "LONGLONGSIZE"
           This symbol contains the size of a long long, so that the C
           preprocessor can make decisions based on it.  It is only defined if
           the system supports long long.

       "LONGSIZE"
           This symbol contains the value of "sizeof(long)" so that the C
           preprocessor can make decisions based on it.

       "memzero"
           Set the "l" bytes starting at *d to all zeroes.

            void  memzero(void * d, Size_t l)

       "NV"
           Described in perlguts.

       "PERL_INT_FAST8_T"
       "PERL_INT_FAST16_T"
       "PERL_UINT_FAST8_T"
       "PERL_UINT_FAST16_T"
           These are equivalent to the correspondingly-named C99 typedefs on
           platforms that have those; they evaluate to "int" and "unsigned
           int" on platforms that don't, so that you can portably take
           advantage of this C99 feature.

       "PERL_INT_MAX"
       "PERL_INT_MIN"
       "PERL_LONG_MAX"
       "PERL_LONG_MIN"
       "PERL_SHORT_MAX"
       "PERL_SHORT_MIN"
       "PERL_UCHAR_MAX"
       "PERL_UCHAR_MIN"
       "PERL_UINT_MAX"
       "PERL_UINT_MIN"
       "PERL_ULONG_MAX"
       "PERL_ULONG_MIN"
       "PERL_USHORT_MAX"
       "PERL_USHORT_MIN"
       "PERL_QUAD_MAX"
       "PERL_QUAD_MIN"
       "PERL_UQUAD_MAX"
       "PERL_UQUAD_MIN"
           These give the largest and smallest number representable in the
           current platform in variables of the corresponding types.

           For signed types, the smallest representable number is the most
           negative number, the one furthest away from zero.

           For C99 and later compilers, these correspond to things like
           "INT_MAX", which are available to the C code.  But these constants,
           furnished by Perl, allow code compiled on earlier compilers to
           portably have access to the same constants.

       "SHORTSIZE"
           This symbol contains the value of "sizeof(short)" so that the C
           preprocessor can make decisions based on it.

       "STRLEN"
           Described in perlguts.

       "U8"
       "U16"
       "U32"
       "U64"
       "UV"
           Described in perlguts.

       "U32SIZE"
           This symbol contains the "sizeof(U32)".

       "U32TYPE"
           This symbol defines the C type used for Perl's U32.

       "U64SIZE"
           This symbol contains the "sizeof(U64)".

       "U64TYPE"
           This symbol defines the C type used for Perl's U64.

       "U16SIZE"
           This symbol contains the "sizeof(U16)".

       "U16TYPE"
           This symbol defines the C type used for Perl's U16.

       "UINT16_C"
       "UINT32_C"
       "UINT64_C"
           Returns a token the C compiler recognizes for the constant "number"
           of the corresponding unsigned integer type on the machine.

           If the machine does not have a 64-bit type, "UINT64_C" is
           undefined.  Use "UINTMAX_C" to get the largest type available on
           the platform.

            U16  UINT16_C(number)
            U32  UINT32_C(number)
            U64  UINT64_C(number)

       "UINTMAX_C"
           Returns a token the C compiler recognizes for the constant "number"
           of the widest unsigned integer type on the machine.  For example,
           if the machine has "long"s, UINTMAX_C(1) would yield

            1UL

           See also, for example, "UINT32_C".

           Use "UV" to declare variables of the maximum usable size on this
           platform.

              UINTMAX_C(number)

       "U8SIZE"
           This symbol contains the "sizeof(U8)".

       "U8TYPE"
           This symbol defines the C type used for Perl's U8.

       "UV_MAX"
           The largest unsigned integer that fits in a UV on this platform.

            UV  UV_MAX

       "UV_MIN"
           The smallest unsigned integer that fits in a UV on this platform.
           It should equal zero.

            UV  UV_MIN

       "UVSIZE"
           This symbol contains the "sizeof(UV)".

       "UVTYPE"
           This symbol defines the C type used for Perl's UV.

       "WIDEST_UTYPE"
           Yields the widest unsigned integer type on the platform, currently
           either "U32" or "U64".  This can be used in declarations such as

            WIDEST_UTYPE my_uv;

           or casts

            my_uv = (WIDEST_UTYPE) val;


Lexer interface

       This is the lower layer of the Perl parser, managing characters and
       tokens.

       "lex_bufutf8"
           NOTE: "lex_bufutf8" is experimental and may change or be removed
           without notice.

           Indicates whether the octets in the lexer buffer
           ("PL_parser->linestr") should be interpreted as the UTF-8 encoding
           of Unicode characters.  If not, they should be interpreted as
           Latin-1 characters.  This is analogous to the "SvUTF8" flag for
           scalars.

           In UTF-8 mode, it is not guaranteed that the lexer buffer actually
           contains valid UTF-8.  Lexing code must be robust in the face of
           invalid encoding.

           The actual "SvUTF8" flag of the "PL_parser->linestr" scalar is
           significant, but not the whole story regarding the input character
           encoding.  Normally, when a file is being read, the scalar contains
           octets and its "SvUTF8" flag is off, but the octets should be
           interpreted as UTF-8 if the "use utf8" pragma is in effect.  During
           a string eval, however, the scalar may have the "SvUTF8" flag on,
           and in this case its octets should be interpreted as UTF-8 unless
           the "use bytes" pragma is in effect.  This logic may change in the
           future; use this function instead of implementing the logic
           yourself.

            bool  lex_bufutf8()

       "lex_discard_to"
           NOTE: "lex_discard_to" is experimental and may change or be removed
           without notice.

           Discards the first part of the "PL_parser->linestr" buffer, up to
           "ptr".  The remaining content of the buffer will be moved, and all
           pointers into the buffer updated appropriately.  "ptr" must not be
           later in the buffer than the position of "PL_parser->bufptr": it is
           not permitted to discard text that has yet to be lexed.

           Normally it is not necessarily to do this directly, because it
           suffices to use the implicit discarding behaviour of
           "lex_next_chunk" and things based on it.  However, if a token
           stretches across multiple lines, and the lexing code has kept
           multiple lines of text in the buffer for that purpose, then after
           completion of the token it would be wise to explicitly discard the
           now-unneeded earlier lines, to avoid future multi-line tokens
           growing the buffer without bound.

            void  lex_discard_to(char* ptr)

       "lex_grow_linestr"
           NOTE: "lex_grow_linestr" is experimental and may change or be
           removed without notice.

           Reallocates the lexer buffer ("PL_parser->linestr") to accommodate
           at least "len" octets (including terminating "NUL").  Returns a
           pointer to the reallocated buffer.  This is necessary before making
           any direct modification of the buffer that would increase its
           length.  "lex_stuff_pvn" provides a more convenient way to insert
           text into the buffer.

           Do not use "SvGROW" or "sv_grow" directly on "PL_parser->linestr";
           this function updates all of the lexer's variables that point
           directly into the buffer.

            char*  lex_grow_linestr(STRLEN len)

       "lex_next_chunk"
           NOTE: "lex_next_chunk" is experimental and may change or be removed
           without notice.

           Reads in the next chunk of text to be lexed, appending it to
           "PL_parser->linestr".  This should be called when lexing code has
           looked to the end of the current chunk and wants to know more.  It
           is usual, but not necessary, for lexing to have consumed the
           entirety of the current chunk at this time.

           If "PL_parser->bufptr" is pointing to the very end of the current
           chunk (i.e., the current chunk has been entirely consumed),
           normally the current chunk will be discarded at the same time that
           the new chunk is read in.  If "flags" has the "LEX_KEEP_PREVIOUS"
           bit set, the current chunk will not be discarded.  If the current
           chunk has not been entirely consumed, then it will not be discarded
           regardless of the flag.

           Returns true if some new text was added to the buffer, or false if
           the buffer has reached the end of the input text.

            bool  lex_next_chunk(U32 flags)

       "lex_peek_unichar"
           NOTE: "lex_peek_unichar" is experimental and may change or be
           removed without notice.

           Looks ahead one (Unicode) character in the text currently being
           lexed.  Returns the codepoint (unsigned integer value) of the next
           character, or -1 if lexing has reached the end of the input text.
           To consume the peeked character, use "lex_read_unichar".

           If the next character is in (or extends into) the next chunk of
           input text, the next chunk will be read in.  Normally the current
           chunk will be discarded at the same time, but if "flags" has the
           "LEX_KEEP_PREVIOUS" bit set, then the current chunk will not be
           discarded.

           If the input is being interpreted as UTF-8 and a UTF-8 encoding
           error is encountered, an exception is generated.

            I32  lex_peek_unichar(U32 flags)

       "lex_read_space"
           NOTE: "lex_read_space" is experimental and may change or be removed
           without notice.

           Reads optional spaces, in Perl style, in the text currently being
           lexed.  The spaces may include ordinary whitespace characters and
           Perl-style comments.  "#line" directives are processed if
           encountered.  "PL_parser->bufptr" is moved past the spaces, so that
           it points at a non-space character (or the end of the input text).

           If spaces extend into the next chunk of input text, the next chunk
           will be read in.  Normally the current chunk will be discarded at
           the same time, but if "flags" has the "LEX_KEEP_PREVIOUS" bit set,
           then the current chunk will not be discarded.

            void  lex_read_space(U32 flags)

       "lex_read_to"
           NOTE: "lex_read_to" is experimental and may change or be removed
           without notice.

           Consume text in the lexer buffer, from "PL_parser->bufptr" up to
           "ptr".  This advances "PL_parser->bufptr" to match "ptr",
           performing the correct bookkeeping whenever a newline character is
           passed.  This is the normal way to consume lexed text.

           Interpretation of the buffer's octets can be abstracted out by
           using the slightly higher-level functions "lex_peek_unichar" and
           "lex_read_unichar".

            void  lex_read_to(char* ptr)

       "lex_read_unichar"
           NOTE: "lex_read_unichar" is experimental and may change or be
           removed without notice.

           Reads the next (Unicode) character in the text currently being
           lexed.  Returns the codepoint (unsigned integer value) of the
           character read, and moves "PL_parser->bufptr" past the character,
           or returns -1 if lexing has reached the end of the input text.  To
           non-destructively examine the next character, use
           "lex_peek_unichar" instead.

           If the next character is in (or extends into) the next chunk of
           input text, the next chunk will be read in.  Normally the current
           chunk will be discarded at the same time, but if "flags" has the
           "LEX_KEEP_PREVIOUS" bit set, then the current chunk will not be
           discarded.

           If the input is being interpreted as UTF-8 and a UTF-8 encoding
           error is encountered, an exception is generated.

            I32  lex_read_unichar(U32 flags)

       "lex_start"
           NOTE: "lex_start" is experimental and may change or be removed
           without notice.

           Creates and initialises a new lexer/parser state object, supplying
           a context in which to lex and parse from a new source of Perl code.
           A pointer to the new state object is placed in "PL_parser".  An
           entry is made on the save stack so that upon unwinding, the new
           state object will be destroyed and the former value of "PL_parser"
           will be restored.  Nothing else need be done to clean up the
           parsing context.

           The code to be parsed comes from "line" and "rsfp".  "line", if
           non-null, provides a string (in SV form) containing code to be
           parsed.  A copy of the string is made, so subsequent modification
           of "line" does not affect parsing.  "rsfp", if non-null, provides
           an input stream from which code will be read to be parsed.  If both
           are non-null, the code in "line" comes first and must consist of
           complete lines of input, and "rsfp" supplies the remainder of the
           source.

           The "flags" parameter is reserved for future use.  Currently it is
           only used by perl internally, so extensions should always pass
           zero.

            void  lex_start(SV* line, PerlIO *rsfp, U32 flags)

       "lex_stuff_pv"
           NOTE: "lex_stuff_pv" is experimental and may change or be removed
           without notice.

           Insert characters into the lexer buffer ("PL_parser->linestr"),
           immediately after the current lexing point ("PL_parser->bufptr"),
           reallocating the buffer if necessary.  This means that lexing code
           that runs later will see the characters as if they had appeared in
           the input.  It is not recommended to do this as part of normal
           parsing, and most uses of this facility run the risk of the
           inserted characters being interpreted in an unintended manner.

           The string to be inserted is represented by octets starting at "pv"
           and continuing to the first nul.  These octets are interpreted as
           either UTF-8 or Latin-1, according to whether the "LEX_STUFF_UTF8"
           flag is set in "flags".  The characters are recoded for the lexer
           buffer, according to how the buffer is currently being interpreted
           ("lex_bufutf8").  If it is not convenient to nul-terminate a string
           to be inserted, the "lex_stuff_pvn" function is more appropriate.

            void  lex_stuff_pv(const char* pv, U32 flags)

       "lex_stuff_pvn"
           NOTE: "lex_stuff_pvn" is experimental and may change or be removed
           without notice.

           Insert characters into the lexer buffer ("PL_parser->linestr"),
           immediately after the current lexing point ("PL_parser->bufptr"),
           reallocating the buffer if necessary.  This means that lexing code
           that runs later will see the characters as if they had appeared in
           the input.  It is not recommended to do this as part of normal
           parsing, and most uses of this facility run the risk of the
           inserted characters being interpreted in an unintended manner.

           The string to be inserted is represented by "len" octets starting
           at "pv".  These octets are interpreted as either UTF-8 or Latin-1,
           according to whether the "LEX_STUFF_UTF8" flag is set in "flags".
           The characters are recoded for the lexer buffer, according to how
           the buffer is currently being interpreted ("lex_bufutf8").  If a
           string to be inserted is available as a Perl scalar, the
           "lex_stuff_sv" function is more convenient.

            void  lex_stuff_pvn(const char* pv, STRLEN len, U32 flags)

       "lex_stuff_pvs"
           NOTE: "lex_stuff_pvs" is experimental and may change or be removed
           without notice.

           Like "lex_stuff_pvn", but takes a literal string instead of a
           string/length pair.

            void  lex_stuff_pvs("pv", U32 flags)

       "lex_stuff_sv"
           NOTE: "lex_stuff_sv" is experimental and may change or be removed
           without notice.

           Insert characters into the lexer buffer ("PL_parser->linestr"),
           immediately after the current lexing point ("PL_parser->bufptr"),
           reallocating the buffer if necessary.  This means that lexing code
           that runs later will see the characters as if they had appeared in
           the input.  It is not recommended to do this as part of normal
           parsing, and most uses of this facility run the risk of the
           inserted characters being interpreted in an unintended manner.

           The string to be inserted is the string value of "sv".  The
           characters are recoded for the lexer buffer, according to how the
           buffer is currently being interpreted ("lex_bufutf8").  If a string
           to be inserted is not already a Perl scalar, the "lex_stuff_pvn"
           function avoids the need to construct a scalar.

            void  lex_stuff_sv(SV* sv, U32 flags)

       "lex_unstuff"
           NOTE: "lex_unstuff" is experimental and may change or be removed
           without notice.

           Discards text about to be lexed, from "PL_parser->bufptr" up to
           "ptr".  Text following "ptr" will be moved, and the buffer
           shortened.  This hides the discarded text from any lexing code that
           runs later, as if the text had never appeared.

           This is not the normal way to consume lexed text.  For that, use
           "lex_read_to".

            void  lex_unstuff(char* ptr)

       "parse_arithexpr"
           NOTE: "parse_arithexpr" is experimental and may change or be
           removed without notice.

           Parse a Perl arithmetic expression.  This may contain operators of
           precedence down to the bit shift operators.  The expression must be
           followed (and thus terminated) either by a comparison or lower-
           precedence operator or by something that would normally terminate
           an expression such as semicolon.  If "flags" has the
           "PARSE_OPTIONAL" bit set, then the expression is optional,
           otherwise it is mandatory.  It is up to the caller to ensure that
           the dynamic parser state ("PL_parser" et al) is correctly set to
           reflect the source of the code to be parsed and the lexical context
           for the expression.

           The op tree representing the expression is returned.  If an
           optional expression is absent, a null pointer is returned,
           otherwise the pointer will be non-null.

           If an error occurs in parsing or compilation, in most cases a valid
           op tree is returned anyway.  The error is reflected in the parser
           state, normally resulting in a single exception at the top level of
           parsing which covers all the compilation errors that occurred.
           Some compilation errors, however, will throw an exception
           immediately.

            OP*  parse_arithexpr(U32 flags)

       "parse_barestmt"
           NOTE: "parse_barestmt" is experimental and may change or be removed
           without notice.

           Parse a single unadorned Perl statement.  This may be a normal
           imperative statement or a declaration that has compile-time effect.
           It does not include any label or other affixture.  It is up to the
           caller to ensure that the dynamic parser state ("PL_parser" et al)
           is correctly set to reflect the source of the code to be parsed and
           the lexical context for the statement.

           The op tree representing the statement is returned.  This may be a
           null pointer if the statement is null, for example if it was
           actually a subroutine definition (which has compile-time side
           effects).  If not null, it will be ops directly implementing the
           statement, suitable to pass to "newSTATEOP".  It will not normally
           include a "nextstate" or equivalent op (except for those embedded
           in a scope contained entirely within the statement).

           If an error occurs in parsing or compilation, in most cases a valid
           op tree (most likely null) is returned anyway.  The error is
           reflected in the parser state, normally resulting in a single
           exception at the top level of parsing which covers all the
           compilation errors that occurred.  Some compilation errors,
           however, will throw an exception immediately.

           The "flags" parameter is reserved for future use, and must always
           be zero.

            OP*  parse_barestmt(U32 flags)

       "parse_block"
           NOTE: "parse_block" is experimental and may change or be removed
           without notice.

           Parse a single complete Perl code block.  This consists of an
           opening brace, a sequence of statements, and a closing brace.  The
           block constitutes a lexical scope, so "my" variables and various
           compile-time effects can be contained within it.  It is up to the
           caller to ensure that the dynamic parser state ("PL_parser" et al)
           is correctly set to reflect the source of the code to be parsed and
           the lexical context for the statement.

           The op tree representing the code block is returned.  This is
           always a real op, never a null pointer.  It will normally be a
           "lineseq" list, including "nextstate" or equivalent ops.  No ops to
           construct any kind of runtime scope are included by virtue of it
           being a block.

           If an error occurs in parsing or compilation, in most cases a valid
           op tree (most likely null) is returned anyway.  The error is
           reflected in the parser state, normally resulting in a single
           exception at the top level of parsing which covers all the
           compilation errors that occurred.  Some compilation errors,
           however, will throw an exception immediately.

           The "flags" parameter is reserved for future use, and must always
           be zero.

            OP*  parse_block(U32 flags)

       "parse_fullexpr"
           NOTE: "parse_fullexpr" is experimental and may change or be removed
           without notice.

           Parse a single complete Perl expression.  This allows the full
           expression grammar, including the lowest-precedence operators such
           as "or".  The expression must be followed (and thus terminated) by
           a token that an expression would normally be terminated by: end-of-
           file, closing bracketing punctuation, semicolon, or one of the
           keywords that signals a postfix expression-statement modifier.  If
           "flags" has the "PARSE_OPTIONAL" bit set, then the expression is
           optional, otherwise it is mandatory.  It is up to the caller to
           ensure that the dynamic parser state ("PL_parser" et al) is
           correctly set to reflect the source of the code to be parsed and
           the lexical context for the expression.

           The op tree representing the expression is returned.  If an
           optional expression is absent, a null pointer is returned,
           otherwise the pointer will be non-null.

           If an error occurs in parsing or compilation, in most cases a valid
           op tree is returned anyway.  The error is reflected in the parser
           state, normally resulting in a single exception at the top level of
           parsing which covers all the compilation errors that occurred.
           Some compilation errors, however, will throw an exception
           immediately.

            OP*  parse_fullexpr(U32 flags)

       "parse_fullstmt"
           NOTE: "parse_fullstmt" is experimental and may change or be removed
           without notice.

           Parse a single complete Perl statement.  This may be a normal
           imperative statement or a declaration that has compile-time effect,
           and may include optional labels.  It is up to the caller to ensure
           that the dynamic parser state ("PL_parser" et al) is correctly set
           to reflect the source of the code to be parsed and the lexical
           context for the statement.

           The op tree representing the statement is returned.  This may be a
           null pointer if the statement is null, for example if it was
           actually a subroutine definition (which has compile-time side
           effects).  If not null, it will be the result of a "newSTATEOP"
           call, normally including a "nextstate" or equivalent op.

           If an error occurs in parsing or compilation, in most cases a valid
           op tree (most likely null) is returned anyway.  The error is
           reflected in the parser state, normally resulting in a single
           exception at the top level of parsing which covers all the
           compilation errors that occurred.  Some compilation errors,
           however, will throw an exception immediately.

           The "flags" parameter is reserved for future use, and must always
           be zero.

            OP*  parse_fullstmt(U32 flags)

       "parse_label"
           NOTE: "parse_label" is experimental and may change or be removed
           without notice.

           Parse a single label, possibly optional, of the type that may
           prefix a Perl statement.  It is up to the caller to ensure that the
           dynamic parser state ("PL_parser" et al) is correctly set to
           reflect the source of the code to be parsed.  If "flags" has the
           "PARSE_OPTIONAL" bit set, then the label is optional, otherwise it
           is mandatory.

           The name of the label is returned in the form of a fresh scalar.
           If an optional label is absent, a null pointer is returned.

           If an error occurs in parsing, which can only occur if the label is
           mandatory, a valid label is returned anyway.  The error is
           reflected in the parser state, normally resulting in a single
           exception at the top level of parsing which covers all the
           compilation errors that occurred.

            SV*  parse_label(U32 flags)

       "parse_listexpr"
           NOTE: "parse_listexpr" is experimental and may change or be removed
           without notice.

           Parse a Perl list expression.  This may contain operators of
           precedence down to the comma operator.  The expression must be
           followed (and thus terminated) either by a low-precedence logic
           operator such as "or" or by something that would normally terminate
           an expression such as semicolon.  If "flags" has the
           "PARSE_OPTIONAL" bit set, then the expression is optional,
           otherwise it is mandatory.  It is up to the caller to ensure that
           the dynamic parser state ("PL_parser" et al) is correctly set to
           reflect the source of the code to be parsed and the lexical context
           for the expression.

           The op tree representing the expression is returned.  If an
           optional expression is absent, a null pointer is returned,
           otherwise the pointer will be non-null.

           If an error occurs in parsing or compilation, in most cases a valid
           op tree is returned anyway.  The error is reflected in the parser
           state, normally resulting in a single exception at the top level of
           parsing which covers all the compilation errors that occurred.
           Some compilation errors, however, will throw an exception
           immediately.

            OP*  parse_listexpr(U32 flags)

       "parse_stmtseq"
           NOTE: "parse_stmtseq" is experimental and may change or be removed
           without notice.

           Parse a sequence of zero or more Perl statements.  These may be
           normal imperative statements, including optional labels, or
           declarations that have compile-time effect, or any mixture thereof.
           The statement sequence ends when a closing brace or end-of-file is
           encountered in a place where a new statement could have validly
           started.  It is up to the caller to ensure that the dynamic parser
           state ("PL_parser" et al) is correctly set to reflect the source of
           the code to be parsed and the lexical context for the statements.

           The op tree representing the statement sequence is returned.  This
           may be a null pointer if the statements were all null, for example
           if there were no statements or if there were only subroutine
           definitions (which have compile-time side effects).  If not null,
           it will be a "lineseq" list, normally including "nextstate" or
           equivalent ops.

           If an error occurs in parsing or compilation, in most cases a valid
           op tree is returned anyway.  The error is reflected in the parser
           state, normally resulting in a single exception at the top level of
           parsing which covers all the compilation errors that occurred.
           Some compilation errors, however, will throw an exception
           immediately.

           The "flags" parameter is reserved for future use, and must always
           be zero.

            OP*  parse_stmtseq(U32 flags)

       "parse_subsignature"
           NOTE: "parse_subsignature" is experimental and may change or be
           removed without notice.

           Parse a subroutine signature declaration. This is the contents of
           the parentheses following a named or anonymous subroutine
           declaration when the "signatures" feature is enabled. Note that
           this function neither expects nor consumes the opening and closing
           parentheses around the signature; it is the caller's job to handle
           these.

           This function must only be called during parsing of a subroutine;
           after "start_subparse" has been called. It might allocate lexical
           variables on the pad for the current subroutine.

           The op tree to unpack the arguments from the stack at runtime is
           returned.  This op tree should appear at the beginning of the
           compiled function. The caller may wish to use "op_append_list" to
           build their function body after it, or splice it together with the
           body before calling "newATTRSUB".

           The "flags" parameter is reserved for future use, and must always
           be zero.

            OP*  parse_subsignature(U32 flags)

       "parse_termexpr"
           NOTE: "parse_termexpr" is experimental and may change or be removed
           without notice.

           Parse a Perl term expression.  This may contain operators of
           precedence down to the assignment operators.  The expression must
           be followed (and thus terminated) either by a comma or lower-
           precedence operator or by something that would normally terminate
           an expression such as semicolon.  If "flags" has the
           "PARSE_OPTIONAL" bit set, then the expression is optional,
           otherwise it is mandatory.  It is up to the caller to ensure that
           the dynamic parser state ("PL_parser" et al) is correctly set to
           reflect the source of the code to be parsed and the lexical context
           for the expression.

           The op tree representing the expression is returned.  If an
           optional expression is absent, a null pointer is returned,
           otherwise the pointer will be non-null.

           If an error occurs in parsing or compilation, in most cases a valid
           op tree is returned anyway.  The error is reflected in the parser
           state, normally resulting in a single exception at the top level of
           parsing which covers all the compilation errors that occurred.
           Some compilation errors, however, will throw an exception
           immediately.

            OP*  parse_termexpr(U32 flags)

       "PL_parser"
           Pointer to a structure encapsulating the state of the parsing
           operation currently in progress.  The pointer can be locally
           changed to perform a nested parse without interfering with the
           state of an outer parse.  Individual members of "PL_parser" have
           their own documentation.

       "PL_parser->bufend"
           NOTE: "PL_parser->bufend" is experimental and may change or be
           removed without notice.

           Direct pointer to the end of the chunk of text currently being
           lexed, the end of the lexer buffer.  This is equal to
           "SvPVX(PL_parser->linestr) + SvCUR(PL_parser->linestr)".  A "NUL"
           character (zero octet) is always located at the end of the buffer,
           and does not count as part of the buffer's contents.

       "PL_parser->bufptr"
           NOTE: "PL_parser->bufptr" is experimental and may change or be
           removed without notice.

           Points to the current position of lexing inside the lexer buffer.
           Characters around this point may be freely examined, within the
           range delimited by "SvPVX("PL_parser->linestr")" and
           "PL_parser->bufend".  The octets of the buffer may be intended to
           be interpreted as either UTF-8 or Latin-1, as indicated by
           "lex_bufutf8".

           Lexing code (whether in the Perl core or not) moves this pointer
           past the characters that it consumes.  It is also expected to
           perform some bookkeeping whenever a newline character is consumed.
           This movement can be more conveniently performed by the function
           "lex_read_to", which handles newlines appropriately.

           Interpretation of the buffer's octets can be abstracted out by
           using the slightly higher-level functions "lex_peek_unichar" and
           "lex_read_unichar".

       "PL_parser->linestart"
           NOTE: "PL_parser->linestart" is experimental and may change or be
           removed without notice.

           Points to the start of the current line inside the lexer buffer.
           This is useful for indicating at which column an error occurred,
           and not much else.  This must be updated by any lexing code that
           consumes a newline; the function "lex_read_to" handles this detail.

       "PL_parser->linestr"
           NOTE: "PL_parser->linestr" is experimental and may change or be
           removed without notice.

           Buffer scalar containing the chunk currently under consideration of
           the text currently being lexed.  This is always a plain string
           scalar (for which "SvPOK" is true).  It is not intended to be used
           as a scalar by normal scalar means; instead refer to the buffer
           directly by the pointer variables described below.

           The lexer maintains various "char*" pointers to things in the
           "PL_parser->linestr" buffer.  If "PL_parser->linestr" is ever
           reallocated, all of these pointers must be updated.  Don't attempt
           to do this manually, but rather use "lex_grow_linestr" if you need
           to reallocate the buffer.

           The content of the text chunk in the buffer is commonly exactly one
           complete line of input, up to and including a newline terminator,
           but there are situations where it is otherwise.  The octets of the
           buffer may be intended to be interpreted as either UTF-8 or
           Latin-1.  The function "lex_bufutf8" tells you which.  Do not use
           the "SvUTF8" flag on this scalar, which may disagree with it.

           For direct examination of the buffer, the variable
           "PL_parser->bufend" points to the end of the buffer.  The current
           lexing position is pointed to by "PL_parser->bufptr".  Direct use
           of these pointers is usually preferable to examination of the
           scalar through normal scalar means.

       "wrap_keyword_plugin"
           NOTE: "wrap_keyword_plugin" is experimental and may change or be
           removed without notice.

           Puts a C function into the chain of keyword plugins.  This is the
           preferred way to manipulate the "PL_keyword_plugin" variable.
           "new_plugin" is a pointer to the C function that is to be added to
           the keyword plugin chain, and "old_plugin_p" points to the storage
           location where a pointer to the next function in the chain will be
           stored.  The value of "new_plugin" is written into the
           "PL_keyword_plugin" variable, while the value previously stored
           there is written to *old_plugin_p.

           "PL_keyword_plugin" is global to an entire process, and a module
           wishing to hook keyword parsing may find itself invoked more than
           once per process, typically in different threads.  To handle that
           situation, this function is idempotent.  The location *old_plugin_p
           must initially (once per process) contain a null pointer.  A C
           variable of static duration (declared at file scope, typically also
           marked "static" to give it internal linkage) will be implicitly
           initialised appropriately, if it does not have an explicit
           initialiser.  This function will only actually modify the plugin
           chain if it finds *old_plugin_p to be null.  This function is also
           thread safe on the small scale.  It uses appropriate locking to
           avoid race conditions in accessing "PL_keyword_plugin".

           When this function is called, the function referenced by
           "new_plugin" must be ready to be called, except for *old_plugin_p
           being unfilled.  In a threading situation, "new_plugin" may be
           called immediately, even before this function has returned.
           *old_plugin_p will always be appropriately set before "new_plugin"
           is called.  If "new_plugin" decides not to do anything special with
           the identifier that it is given (which is the usual case for most
           calls to a keyword plugin), it must chain the plugin function
           referenced by *old_plugin_p.

           Taken all together, XS code to install a keyword plugin should
           typically look something like this:

               static Perl_keyword_plugin_t next_keyword_plugin;
               static OP *my_keyword_plugin(pTHX_
                   char *keyword_ptr, STRLEN keyword_len, OP **op_ptr)
               {
                   if (memEQs(keyword_ptr, keyword_len,
                              "my_new_keyword")) {
                       ...
                   } else {
                       return next_keyword_plugin(aTHX_
                           keyword_ptr, keyword_len, op_ptr);
                   }
               }
               BOOT:
                   wrap_keyword_plugin(my_keyword_plugin,
                                       &next_keyword_plugin);

           Direct access to "PL_keyword_plugin" should be avoided.

            void  wrap_keyword_plugin(Perl_keyword_plugin_t new_plugin,
                                      Perl_keyword_plugin_t *old_plugin_p)


Locales

       "DECLARATION_FOR_LC_NUMERIC_MANIPULATION"
           This macro should be used as a statement.  It declares a private
           variable (whose name begins with an underscore) that is needed by
           the other macros in this section.  Failing to include this
           correctly should lead to a syntax error.  For compatibility with
           C89 C compilers it should be placed in a block before any
           executable statements.

            void  DECLARATION_FOR_LC_NUMERIC_MANIPULATION

       "foldEQ_locale"
           Returns true if the leading "len" bytes of the strings "s1" and
           "s2" are the same case-insensitively in the current locale; false
           otherwise.

            I32  foldEQ_locale(const char* a, const char* b, I32 len)

       "HAS_DUPLOCALE"
           This symbol, if defined, indicates that the "duplocale" routine is
           available to duplicate a locale object.

       "HAS_FREELOCALE"
           This symbol, if defined, indicates that the "freelocale" routine is
           available to deallocates the resources associated with a locale
           object.

       "HAS_LC_MONETARY_2008"
           This symbol, if defined, indicates that the localeconv routine is
           available and has the additional members added in "POSIX"
           1003.1-2008.

       "HAS_LOCALECONV"
           This symbol, if defined, indicates that the "localeconv" routine is
           available for numeric and monetary formatting conventions.

       "HAS_LOCALECONV_L"
           This symbol, if defined, indicates that the "localeconv_l" routine
           is available to query certain information about a locale.

       "HAS_NEWLOCALE"
           This symbol, if defined, indicates that the "newlocale" routine is
           available to return a new locale object or modify an existing
           locale object.

       "HAS_NL_LANGINFO"
           This symbol, if defined, indicates that the "nl_langinfo" routine
           is available to return local data.  You will also need langinfo.h
           and therefore "I_LANGINFO".

       "HAS_QUERYLOCALE"
           This symbol, if defined, indicates that the "querylocale" routine
           is available to return the name of the locale for a category mask.

       "HAS_SETLOCALE"
           This symbol, if defined, indicates that the "setlocale" routine is
           available to handle locale-specific ctype implementations.

       "HAS_SETLOCALE_R"
           This symbol, if defined, indicates that the "setlocale_r" routine
           is available to setlocale re-entrantly.

       "HAS_THREAD_SAFE_NL_LANGINFO_L"
           This symbol, when defined, indicates presence of the
           "nl_langinfo_l()" function, and that it is thread-safe.

       "HAS_USELOCALE"
           This symbol, if defined, indicates that the "uselocale" routine is
           available to set the current locale for the calling thread.

       "I_LANGINFO"
           This symbol, if defined, indicates that langinfo.h exists and
           should be included.

            #ifdef I_LANGINFO
                #include <langinfo.h>
            #endif

       "I_LOCALE"
           This symbol, if defined, indicates to the C program that it should
           include locale.h.

            #ifdef I_LOCALE
                #include <locale.h>
            #endif

       "IN_LOCALE"
           Evaluates to TRUE if the plain locale pragma without a parameter
           ("use locale") is in effect.

            bool  IN_LOCALE

       "IN_LOCALE_COMPILETIME"
           Evaluates to TRUE if, when compiling a perl program (including an
           "eval") if the plain locale pragma without a parameter
           ("use locale") is in effect.

            bool  IN_LOCALE_COMPILETIME

       "IN_LOCALE_RUNTIME"
           Evaluates to TRUE if, when executing a perl program (including an
           "eval") if the plain locale pragma without a parameter
           ("use locale") is in effect.

            bool  IN_LOCALE_RUNTIME

       "I_XLOCALE"
           This symbol, if defined, indicates to the C program that it should
           include xlocale.h to get "uselocale()" and its friends.

            #ifdef I_XLOCALE
                #include <xlocale.h>
            #endif

       "Perl_langinfo"
           This is an (almost) drop-in replacement for the system
           nl_langinfo(3), taking the same "item" parameter values, and
           returning the same information.  But it is more thread-safe than
           regular "nl_langinfo()", and hides the quirks of Perl's locale
           handling from your code, and can be used on systems that lack a
           native "nl_langinfo".

           Expanding on these:

           o   The reason it isn't quite a drop-in replacement is actually an
               advantage.  The only difference is that it returns
               "const char *", whereas plain "nl_langinfo()" returns "char *",
               but you are (only by documentation) forbidden to write into the
               buffer.  By declaring this "const", the compiler enforces this
               restriction, so if it is violated, you know at compilation
               time, rather than getting segfaults at runtime.

           o   It delivers the correct results for the "RADIXCHAR" and
               "THOUSEP" items, without you having to write extra code.  The
               reason for the extra code would be because these are from the
               "LC_NUMERIC" locale category, which is normally kept set by
               Perl so that the radix is a dot, and the separator is the empty
               string, no matter what the underlying locale is supposed to be,
               and so to get the expected results, you have to temporarily
               toggle into the underlying locale, and later toggle back.  (You
               could use plain "nl_langinfo" and
               "STORE_LC_NUMERIC_FORCE_TO_UNDERLYING" for this but then you
               wouldn't get the other advantages of "Perl_langinfo()"; not
               keeping "LC_NUMERIC" in the C (or equivalent) locale would
               break a lot of CPAN, which is expecting the radix (decimal
               point) character to be a dot.)

           o   The system function it replaces can have its static return
               buffer trashed, not only by a subsequent call to that function,
               but by a "freelocale", "setlocale", or other locale change.
               The returned buffer of this function is not changed until the
               next call to it, so the buffer is never in a trashed state.

           o   Its return buffer is per-thread, so it also is never
               overwritten by a call to this function from another thread;
               unlike the function it replaces.

           o   But most importantly, it works on systems that don't have
               "nl_langinfo", such as Windows, hence makes your code more
               portable.  Of the fifty-some possible items specified by the
               POSIX 2008 standard,
               <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/langinfo.h.html>,
               only one is completely unimplemented, though on non-Windows
               platforms, another significant one is also not implemented).
               It uses various techniques to recover the other items,
               including calling localeconv(3), and strftime(3), both of which
               are specified in C89, so should be always be available.  Later
               "strftime()" versions have additional capabilities; "" is
               returned for those not available on your system.

               It is important to note that when called with an item that is
               recovered by using "localeconv", the buffer from any previous
               explicit call to "localeconv" will be overwritten.  This means
               you must save that buffer's contents if you need to access them
               after a call to this function.  (But note that you might not
               want to be using "localeconv()" directly anyway, because of
               issues like the ones listed in the second item of this list
               (above) for "RADIXCHAR" and "THOUSEP".  You can use the methods
               given in perlcall to call "localeconv" in POSIX and avoid all
               the issues, but then you have a hash to unpack).

               The details for those items which may deviate from what this
               emulation returns and what a native "nl_langinfo()" would
               return are specified in I18N::Langinfo.

           When using "Perl_langinfo" on systems that don't have a native
           "nl_langinfo()", you must

            #include "perl_langinfo.h"

           before the "perl.h" "#include".  You can replace your "langinfo.h"
           "#include" with this one.  (Doing it this way keeps out the symbols
           that plain "langinfo.h" would try to import into the namespace for
           code that doesn't need it.)

           The original impetus for "Perl_langinfo()" was so that code that
           needs to find out the current currency symbol, floating point radix
           character, or digit grouping separator can use, on all systems, the
           simpler and more thread-friendly "nl_langinfo" API instead of
           localeconv(3) which is a pain to make thread-friendly.  For other
           fields returned by "localeconv", it is better to use the methods
           given in perlcall to call "POSIX::localeconv()", which is thread-
           friendly.

            const char*  Perl_langinfo(const nl_item item)

       "Perl_setlocale"
           This is an (almost) drop-in replacement for the system
           setlocale(3), taking the same parameters, and returning the same
           information, except that it returns the correct underlying
           "LC_NUMERIC" locale.  Regular "setlocale" will instead return "C"
           if the underlying locale has a non-dot decimal point character, or
           a non-empty thousands separator for displaying floating point
           numbers.  This is because perl keeps that locale category such that
           it has a dot and empty separator, changing the locale briefly
           during the operations where the underlying one is required.
           "Perl_setlocale" knows about this, and compensates; regular
           "setlocale" doesn't.

           Another reason it isn't completely a drop-in replacement is that it
           is declared to return "const char *", whereas the system setlocale
           omits the "const" (presumably because its API was specified long
           ago, and can't be updated; it is illegal to change the information
           "setlocale" returns; doing so leads to segfaults.)

           Finally, "Perl_setlocale" works under all circumstances, whereas
           plain "setlocale" can be completely ineffective on some platforms
           under some configurations.

           "Perl_setlocale" should not be used to change the locale except on
           systems where the predefined variable "${^SAFE_LOCALES}" is 1.  On
           some such systems, the system "setlocale()" is ineffective,
           returning the wrong information, and failing to actually change the
           locale.  "Perl_setlocale", however works properly in all
           circumstances.

           The return points to a per-thread static buffer, which is
           overwritten the next time "Perl_setlocale" is called from the same
           thread.

            const char*  Perl_setlocale(const int category,
                                        const char* locale)

       "RESTORE_LC_NUMERIC"
           This is used in conjunction with one of the macros
           "STORE_LC_NUMERIC_SET_TO_NEEDED" and
           "STORE_LC_NUMERIC_FORCE_TO_UNDERLYING" to properly restore the
           "LC_NUMERIC" state.

           A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have been
           made to declare at compile time a private variable used by this
           macro and the two "STORE" ones.  This macro should be called as a
           single statement, not an expression, but with an empty argument
           list, like this:

            {
               DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                ...
               RESTORE_LC_NUMERIC();
                ...
            }

            void  RESTORE_LC_NUMERIC()

       "SETLOCALE_ACCEPTS_ANY_LOCALE_NAME"
           This symbol, if defined, indicates that the setlocale routine is
           available and it accepts any input locale name as valid.

       "STORE_LC_NUMERIC_FORCE_TO_UNDERLYING"
           This is used by XS code that is "LC_NUMERIC" locale-aware to force
           the locale for category "LC_NUMERIC" to be what perl thinks is the
           current underlying locale.  (The perl interpreter could be wrong
           about what the underlying locale actually is if some C or XS code
           has called the C library function setlocale(3) behind its back;
           calling "sync_locale" before calling this macro will update perl's
           records.)

           A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have been
           made to declare at compile time a private variable used by this
           macro.  This macro should be called as a single statement, not an
           expression, but with an empty argument list, like this:

            {
               DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                ...
               STORE_LC_NUMERIC_FORCE_TO_UNDERLYING();
                ...
               RESTORE_LC_NUMERIC();
                ...
            }

           The private variable is used to save the current locale state, so
           that the requisite matching call to "RESTORE_LC_NUMERIC" can
           restore it.

           On threaded perls not operating with thread-safe functionality,
           this macro uses a mutex to force a critical section.  Therefore the
           matching RESTORE should be close by, and guaranteed to be called.

            void  STORE_LC_NUMERIC_FORCE_TO_UNDERLYING()

       "STORE_LC_NUMERIC_SET_TO_NEEDED"
           This is used to help wrap XS or C code that is "LC_NUMERIC" locale-
           aware.  This locale category is generally kept set to a locale
           where the decimal radix character is a dot, and the separator
           between groups of digits is empty.  This is because most XS code
           that reads floating point numbers is expecting them to have this
           syntax.

           This macro makes sure the current "LC_NUMERIC" state is set
           properly, to be aware of locale if the call to the XS or C code
           from the Perl program is from within the scope of a "use locale";
           or to ignore locale if the call is instead from outside such scope.

           This macro is the start of wrapping the C or XS code; the wrap
           ending is done by calling the "RESTORE_LC_NUMERIC" macro after the
           operation.  Otherwise the state can be changed that will adversely
           affect other XS code.

           A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have been
           made to declare at compile time a private variable used by this
           macro.  This macro should be called as a single statement, not an
           expression, but with an empty argument list, like this:

            {
               DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                ...
               STORE_LC_NUMERIC_SET_TO_NEEDED();
                ...
               RESTORE_LC_NUMERIC();
                ...
            }

           On threaded perls not operating with thread-safe functionality,
           this macro uses a mutex to force a critical section.  Therefore the
           matching RESTORE should be close by, and guaranteed to be called;
           see "WITH_LC_NUMERIC_SET_TO_NEEDED" for a more contained way to
           ensure that.

            void  STORE_LC_NUMERIC_SET_TO_NEEDED()

       "STORE_LC_NUMERIC_SET_TO_NEEDED_IN"
           Same as "STORE_LC_NUMERIC_SET_TO_NEEDED" with in_lc_numeric
           provided as the precalculated value of "IN_LC(LC_NUMERIC)". It is
           the caller's responsibility to ensure that the status of
           "PL_compiling" and "PL_hints" cannot have changed since the
           precalculation.

            void  STORE_LC_NUMERIC_SET_TO_NEEDED_IN(bool in_lc_numeric)

       "switch_to_global_locale"
           On systems without locale support, or on typical single-threaded
           builds, or on platforms that do not support per-thread locale
           operations, this function does nothing.  On such systems that do
           have locale support, only a locale global to the whole program is
           available.

           On multi-threaded builds on systems that do have per-thread locale
           operations, this function converts the thread it is running in to
           use the global locale.  This is for code that has not yet or cannot
           be updated to handle multi-threaded locale operation.  As long as
           only a single thread is so-converted, everything works fine, as all
           the other threads continue to ignore the global one, so only this
           thread looks at it.

           However, on Windows systems this isn't quite true prior to Visual
           Studio 15, at which point Microsoft fixed a bug.  A race can occur
           if you use the following operations on earlier Windows platforms:

           POSIX::localeconv
           I18N::Langinfo, items "CRNCYSTR" and "THOUSEP"
           "Perl_langinfo" in perlapi, items "CRNCYSTR" and "THOUSEP"

           The first item is not fixable (except by upgrading to a later
           Visual Studio release), but it would be possible to work around the
           latter two items by using the Windows API functions
           "GetNumberFormat" and "GetCurrencyFormat"; patches welcome.

           Without this function call, threads that use the setlocale(3)
           system function will not work properly, as all the locale-sensitive
           functions will look at the per-thread locale, and "setlocale" will
           have no effect on this thread.

           Perl code should convert to either call "Perl_setlocale" (which is
           a drop-in for the system "setlocale") or use the methods given in
           perlcall to call "POSIX::setlocale".  Either one will transparently
           properly handle all cases of single- vs multi-thread, POSIX
           2008-supported or not.

           Non-Perl libraries, such as "gtk", that call the system "setlocale"
           can continue to work if this function is called before transferring
           control to the library.

           Upon return from the code that needs to use the global locale,
           "sync_locale()" should be called to restore the safe multi-thread
           operation.

            void  switch_to_global_locale()

       "sync_locale"
           "Perl_setlocale" can be used at any time to query or change the
           locale (though changing the locale is antisocial and dangerous on
           multi-threaded systems that don't have multi-thread safe locale
           operations.  (See "Multi-threaded operation" in perllocale).  Using
           the system setlocale(3) should be avoided.  Nevertheless, certain
           non-Perl libraries called from XS, such as "Gtk" do so, and this
           can't be changed.  When the locale is changed by XS code that
           didn't use "Perl_setlocale", Perl needs to be told that the locale
           has changed.  Use this function to do so, before returning to Perl.

           The return value is a boolean: TRUE if the global locale at the
           time of call was in effect; and FALSE if a per-thread locale was in
           effect.  This can be used by the caller that needs to restore
           things as-they-were to decide whether or not to call
           "Perl_switch_to_global_locale".

            bool  sync_locale()

       "WITH_LC_NUMERIC_SET_TO_NEEDED"
           This macro invokes the supplied statement or block within the
           context of a "STORE_LC_NUMERIC_SET_TO_NEEDED" ..
           "RESTORE_LC_NUMERIC" pair if required, so eg:

             WITH_LC_NUMERIC_SET_TO_NEEDED(
               SNPRINTF_G(fv, ebuf, sizeof(ebuf), precis)
             );

           is equivalent to:

             {
           #ifdef USE_LOCALE_NUMERIC
               DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
               STORE_LC_NUMERIC_SET_TO_NEEDED();
           #endif
               SNPRINTF_G(fv, ebuf, sizeof(ebuf), precis);
           #ifdef USE_LOCALE_NUMERIC
               RESTORE_LC_NUMERIC();
           #endif
             }

            void  WITH_LC_NUMERIC_SET_TO_NEEDED(block)

       "WITH_LC_NUMERIC_SET_TO_NEEDED_IN"
           Same as "WITH_LC_NUMERIC_SET_TO_NEEDED" with in_lc_numeric provided
           as the precalculated value of "IN_LC(LC_NUMERIC)". It is the
           caller's responsibility to ensure that the status of "PL_compiling"
           and "PL_hints" cannot have changed since the precalculation.

            void  WITH_LC_NUMERIC_SET_TO_NEEDED_IN(bool in_lc_numeric, block)


Magic

       "Magic" is special data attached to SV structures in order to give them
       "magical" properties.  When any Perl code tries to read from, or assign
       to, an SV marked as magical, it calls the 'get' or 'set' function
       associated with that SV's magic.  A get is called prior to reading an
       SV, in order to give it a chance to update its internal value (get on
       $. writes the line number of the last read filehandle into the SV's IV
       slot), while set is called after an SV has been written to, in order to
       allow it to make use of its changed value (set on $/ copies the SV's
       new value to the PL_rs global variable).

       Magic is implemented as a linked list of MAGIC structures attached to
       the SV.  Each MAGIC struct holds the type of the magic, a pointer to an
       array of functions that implement the get(), set(), length() etc
       functions, plus space for some flags and pointers.  For example, a tied
       variable has a MAGIC structure that contains a pointer to the object
       associated with the tie.

       "mg_clear"
           Clear something magical that the SV represents.  See "sv_magic".

            int  mg_clear(SV* sv)

       "mg_copy"
           Copies the magic from one SV to another.  See "sv_magic".

            int  mg_copy(SV *sv, SV *nsv, const char *key, I32 klen)

       "mg_find"
           Finds the magic pointer for "type" matching the SV.  See
           "sv_magic".

            MAGIC*  mg_find(const SV* sv, int type)

       "mg_findext"
           Finds the magic pointer of "type" with the given "vtbl" for the
           "SV".  See "sv_magicext".

            MAGIC*  mg_findext(const SV* sv, int type, const MGVTBL *vtbl)

       "mg_free"
           Free any magic storage used by the SV.  See "sv_magic".

            int  mg_free(SV* sv)

       "mg_freeext"
           Remove any magic of type "how" using virtual table "vtbl" from the
           SV "sv".  See "sv_magic".

           "mg_freeext(sv, how, NULL)" is equivalent to "mg_free_type(sv,
           how)".

            void  mg_freeext(SV* sv, int how, const MGVTBL *vtbl)

       "mg_free_type"
           Remove any magic of type "how" from the SV "sv".  See "sv_magic".

            void  mg_free_type(SV* sv, int how)

       "mg_get"
           Do magic before a value is retrieved from the SV.  The type of SV
           must be >= "SVt_PVMG".  See "sv_magic".

            int  mg_get(SV* sv)

       "mg_length"
           "DEPRECATED!"  It is planned to remove "mg_length" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Reports on the SV's length in bytes, calling length magic if
           available, but does not set the UTF8 flag on "sv".  It will fall
           back to 'get' magic if there is no 'length' magic, but with no
           indication as to whether it called 'get' magic.  It assumes "sv" is
           a "PVMG" or higher.  Use "sv_len()" instead.

            U32  mg_length(SV* sv)

       "mg_magical"
           Turns on the magical status of an SV.  See "sv_magic".

            void  mg_magical(SV* sv)

       "mg_set"
           Do magic after a value is assigned to the SV.  See "sv_magic".

            int  mg_set(SV* sv)

       "SvTIED_obj"
           Described in perlinterp.

              SvTIED_obj(SV *sv, MAGIC *mg)


Memory Management

       "HASATTRIBUTE_MALLOC"
           Can we handle "GCC" attribute for malloc-style functions.

       "HAS_MALLOC_GOOD_SIZE"
           This symbol, if defined, indicates that the "malloc_good_size"
           routine is available for use.

       "HAS_MALLOC_SIZE"
           This symbol, if defined, indicates that the "malloc_size" routine
           is available for use.

       "I_MALLOCMALLOC"
           This symbol, if defined, indicates to the C program that it should
           include malloc/malloc.h.

            #ifdef I_MALLOCMALLOC
                #include <mallocmalloc.h>
            #endif

       "MYMALLOC"
           This symbol, if defined, indicates that we're using our own malloc.

       "Newx"
           The XSUB-writer's interface to the C "malloc" function.

           Memory obtained by this should ONLY be freed with "Safefree".

           In 5.9.3, Newx() and friends replace the older New() API, and drops
           the first parameter, x, a debug aid which allowed callers to
           identify themselves.  This aid has been superseded by a new build
           option, PERL_MEM_LOG (see "PERL_MEM_LOG" in perlhacktips).  The
           older API is still there for use in XS modules supporting older
           perls.

            void  Newx(void* ptr, int nitems, type)

       "Newxc"
           The XSUB-writer's interface to the C "malloc" function, with cast.
           See also "Newx".

           Memory obtained by this should ONLY be freed with "Safefree".

            void  Newxc(void* ptr, int nitems, type, cast)

       "Newxz"
           The XSUB-writer's interface to the C "malloc" function.  The
           allocated memory is zeroed with "memzero".  See also "Newx".

           Memory obtained by this should ONLY be freed with "Safefree".

            void  Newxz(void* ptr, int nitems, type)

       "PERL_MALLOC_WRAP"
           This symbol, if defined, indicates that we'd like malloc wrap
           checks.

       "Renew"
           The XSUB-writer's interface to the C "realloc" function.

           Memory obtained by this should ONLY be freed with "Safefree".

            void  Renew(void* ptr, int nitems, type)

       "Renewc"
           The XSUB-writer's interface to the C "realloc" function, with cast.

           Memory obtained by this should ONLY be freed with "Safefree".

            void  Renewc(void* ptr, int nitems, type, cast)

       "Safefree"
           The XSUB-writer's interface to the C "free" function.

           This should ONLY be used on memory obtained using "Newx" and
           friends.

            void  Safefree(void* ptr)

       "safesyscalloc"
           Safe version of system's calloc()

            Malloc_t  safesyscalloc(MEM_SIZE elements, MEM_SIZE size)

       "safesysfree"
           Safe version of system's free()

            Free_t  safesysfree(Malloc_t where)

       "safesysmalloc"
           Paranoid version of system's malloc()

            Malloc_t  safesysmalloc(MEM_SIZE nbytes)

       "safesysrealloc"
           Paranoid version of system's realloc()

            Malloc_t  safesysrealloc(Malloc_t where, MEM_SIZE nbytes)


MRO

       These functions are related to the method resolution order of perl
       classes Also see perlmroapi.

       "HvMROMETA"
           Described in perlmroapi.

            struct mro_meta *  HvMROMETA(HV *hv)

       "mro_get_linear_isa"
           Returns the mro linearisation for the given stash.  By default,
           this will be whatever "mro_get_linear_isa_dfs" returns unless some
           other MRO is in effect for the stash.  The return value is a read-
           only AV*.

           You are responsible for "SvREFCNT_inc()" on the return value if you
           plan to store it anywhere semi-permanently (otherwise it might be
           deleted out from under you the next time the cache is invalidated).

            AV*  mro_get_linear_isa(HV* stash)

       "MRO_GET_PRIVATE_DATA"
           Described in perlmroapi.

            SV*  MRO_GET_PRIVATE_DATA(struct mro_meta *const smeta,
                                      const struct mro_alg *const which)

       "mro_method_changed_in"
           Invalidates method caching on any child classes of the given stash,
           so that they might notice the changes in this one.

           Ideally, all instances of "PL_sub_generation++" in perl source
           outside of mro.c should be replaced by calls to this.

           Perl automatically handles most of the common ways a method might
           be redefined.  However, there are a few ways you could change a
           method in a stash without the cache code noticing, in which case
           you need to call this method afterwards:

           1) Directly manipulating the stash HV entries from XS code.

           2) Assigning a reference to a readonly scalar constant into a stash
           entry in order to create a constant subroutine (like constant.pm
           does).

           This same method is available from pure perl via,
           "mro::method_changed_in(classname)".

            void  mro_method_changed_in(HV* stash)

       "mro_register"
           Registers a custom mro plugin.  See perlmroapi for details on this
           and other mro functions.

           NOTE: "mro_register" must be explicitly called as
           "Perl_mro_register" with an "aTHX_" parameter.

            void  Perl_mro_register(pTHX_ const struct mro_alg *mro)

       "mro_set_private_data"
           Described in perlmroapi.

           NOTE: "mro_set_private_data" must be explicitly called as
           "Perl_mro_set_private_data" with an "aTHX_" parameter.

            SV*  Perl_mro_set_private_data(pTHX_
                                           struct mro_meta *const smeta,
                                           const struct mro_alg *const which,
                                           SV *const data)


Multicall Functions

       "dMULTICALL"
           Declare local variables for a multicall.  See "LIGHTWEIGHT
           CALLBACKS" in perlcall.

              dMULTICALL;

       "MULTICALL"
           Make a lightweight callback.  See "LIGHTWEIGHT CALLBACKS" in
           perlcall.

              MULTICALL;

       "POP_MULTICALL"
           Closing bracket for a lightweight callback.  See "LIGHTWEIGHT
           CALLBACKS" in perlcall.

              POP_MULTICALL;

       "PUSH_MULTICALL"
           Opening bracket for a lightweight callback.  See "LIGHTWEIGHT
           CALLBACKS" in perlcall.

              PUSH_MULTICALL(CV* the_cv);


Numeric Functions

       "Drand01"
           This macro is to be used to generate uniformly distributed random
           numbers over the range [0., 1.[.  You may have to supply an 'extern
           double "drand48()";' in your program since SunOS 4.1.3 doesn't
           provide you with anything relevant in its headers.  See
           "HAS_DRAND48_PROTO".

            double  Drand01()

       "Gconvert"
           This preprocessor macro is defined to convert a floating point
           number to a string without a trailing decimal point.  This emulates
           the behavior of "sprintf("%g")", but is sometimes much more
           efficient.  If "gconvert()" is not available, but "gcvt()" drops
           the trailing decimal point, then "gcvt()" is used.  If all else
           fails, a macro using "sprintf("%g")" is used. Arguments for the
           Gconvert macro are: value, number of digits, whether trailing zeros
           should be retained, and the output buffer.  The usual values are:

            d_Gconvert='gconvert((x),(n),(t),(b))'
            d_Gconvert='gcvt((x),(n),(b))'
            d_Gconvert='sprintf((b),"%.*g",(n),(x))'

           The last two assume trailing zeros should not be kept.

            char *  Gconvert(double x, Size_t n, bool t, char * b)

       "grok_bin"
           converts a string representing a binary number to numeric form.

           On entry "start" and *len_p give the string to scan, *flags gives
           conversion flags, and "result" should be "NULL" or a pointer to an
           NV.  The scan stops at the end of the string, or at just before the
           first invalid character.  Unless "PERL_SCAN_SILENT_ILLDIGIT" is set
           in *flags, encountering an invalid character (except NUL) will also
           trigger a warning.  On return *len_p is set to the length of the
           scanned string, and *flags gives output flags.

           If the value is <= "UV_MAX" it is returned as a UV, the output
           flags are clear, and nothing is written to *result.  If the value
           is > "UV_MAX", "grok_bin" returns "UV_MAX", sets
           "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes an
           approximation of the correct value into *result (which is an NV; or
           the approximation is discarded if "result" is NULL).

           The binary number may optionally be prefixed with "0b" or "b"
           unless "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.

           If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then any or all
           pairs of digits may be separated from each other by a single
           underscore; also a single leading underscore is accepted.

            UV  grok_bin(const char* start, STRLEN* len_p, I32* flags,
                         NV *result)

       "grok_hex"
           converts a string representing a hex number to numeric form.

           On entry "start" and *len_p give the string to scan, *flags gives
           conversion flags, and "result" should be "NULL" or a pointer to an
           NV.  The scan stops at the end of the string, or at just before the
           first invalid character.  Unless "PERL_SCAN_SILENT_ILLDIGIT" is set
           in *flags, encountering an invalid character (except NUL) will also
           trigger a warning.  On return *len_p is set to the length of the
           scanned string, and *flags gives output flags.

           If the value is <= "UV_MAX" it is returned as a UV, the output
           flags are clear, and nothing is written to *result.  If the value
           is > "UV_MAX", "grok_hex" returns "UV_MAX", sets
           "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes an
           approximation of the correct value into *result (which is an NV; or
           the approximation is discarded if "result" is NULL).

           The hex number may optionally be prefixed with "0x" or "x" unless
           "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.

           If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then any or all
           pairs of digits may be separated from each other by a single
           underscore; also a single leading underscore is accepted.

            UV  grok_hex(const char* start, STRLEN* len_p, I32* flags,
                         NV *result)

       "grok_infnan"
           Helper for "grok_number()", accepts various ways of spelling
           "infinity" or "not a number", and returns one of the following flag
           combinations:

             IS_NUMBER_INFINITY
             IS_NUMBER_NAN
             IS_NUMBER_INFINITY | IS_NUMBER_NEG
             IS_NUMBER_NAN | IS_NUMBER_NEG
             0

           possibly |-ed with "IS_NUMBER_TRAILING".

           If an infinity or a not-a-number is recognized, *sp will point to
           one byte past the end of the recognized string.  If the recognition
           fails, zero is returned, and *sp will not move.

            int  grok_infnan(const char** sp, const char *send)

       "grok_number"
           Identical to "grok_number_flags()" with "flags" set to zero.

            int  grok_number(const char *pv, STRLEN len, UV *valuep)

       "grok_number_flags"
           Recognise (or not) a number.  The type of the number is returned (0
           if unrecognised), otherwise it is a bit-ORed combination of
           "IS_NUMBER_IN_UV", "IS_NUMBER_GREATER_THAN_UV_MAX",
           "IS_NUMBER_NOT_INT", "IS_NUMBER_NEG", "IS_NUMBER_INFINITY",
           "IS_NUMBER_NAN" (defined in perl.h).

           If the value of the number can fit in a UV, it is returned in
           *valuep.  "IS_NUMBER_IN_UV" will be set to indicate that *valuep is
           valid, "IS_NUMBER_IN_UV" will never be set unless *valuep is valid,
           but *valuep may have been assigned to during processing even though
           "IS_NUMBER_IN_UV" is not set on return.  If "valuep" is "NULL",
           "IS_NUMBER_IN_UV" will be set for the same cases as when "valuep"
           is non-"NULL", but no actual assignment (or SEGV) will occur.

           "IS_NUMBER_NOT_INT" will be set with "IS_NUMBER_IN_UV" if trailing
           decimals were seen (in which case *valuep gives the true value
           truncated to an integer), and "IS_NUMBER_NEG" if the number is
           negative (in which case *valuep holds the absolute value).
           "IS_NUMBER_IN_UV" is not set if "e" notation was used or the number
           is larger than a UV.

           "flags" allows only "PERL_SCAN_TRAILING", which allows for trailing
           non-numeric text on an otherwise successful grok, setting
           "IS_NUMBER_TRAILING" on the result.

            int  grok_number_flags(const char *pv, STRLEN len, UV *valuep,
                                   U32 flags)

       "GROK_NUMERIC_RADIX"
           A synonym for "grok_numeric_radix"

            bool  GROK_NUMERIC_RADIX(NN const char **sp, NN const char *send)

       "grok_numeric_radix"
           Scan and skip for a numeric decimal separator (radix).

            bool  grok_numeric_radix(const char **sp, const char *send)

       "grok_oct"
           converts a string representing an octal number to numeric form.

           On entry "start" and *len_p give the string to scan, *flags gives
           conversion flags, and "result" should be "NULL" or a pointer to an
           NV.  The scan stops at the end of the string, or at just before the
           first invalid character.  Unless "PERL_SCAN_SILENT_ILLDIGIT" is set
           in *flags, encountering an invalid character (except NUL) will also
           trigger a warning.  On return *len_p is set to the length of the
           scanned string, and *flags gives output flags.

           If the value is <= "UV_MAX" it is returned as a UV, the output
           flags are clear, and nothing is written to *result.  If the value
           is > "UV_MAX", "grok_oct" returns "UV_MAX", sets
           "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes an
           approximation of the correct value into *result (which is an NV; or
           the approximation is discarded if "result" is NULL).

           If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then any or all
           pairs of digits may be separated from each other by a single
           underscore; also a single leading underscore is accepted.

           The "PERL_SCAN_DISALLOW_PREFIX" flag is always treated as being set
           for this function.

            UV  grok_oct(const char* start, STRLEN* len_p, I32* flags,
                         NV *result)

       "isinfnan"
           "Perl_isinfnan()" is a utility function that returns true if the NV
           argument is either an infinity or a "NaN", false otherwise.  To
           test in more detail, use "Perl_isinf()" and "Perl_isnan()".

           This is also the logical inverse of Perl_isfinite().

            bool  isinfnan(NV nv)

       "my_atof"
           "atof"(3), but properly works with Perl locale handling, accepting
           a dot radix character always, but also the current locale's radix
           character if and only if called from within the lexical scope of a
           Perl "use locale" statement.

           N.B. "s" must be NUL terminated.

            NV  my_atof(const char *s)

       "my_strtod"
           This function is equivalent to the libc strtod() function, and is
           available even on platforms that lack plain strtod().  Its return
           value is the best available precision depending on platform
           capabilities and Configure options.

           It properly handles the locale radix character, meaning it expects
           a dot except when called from within the scope of "use locale", in
           which case the radix character should be that specified by the
           current locale.

           The synonym Strtod() may be used instead.

            NV  my_strtod(const char * const s, char ** e)

       "PERL_ABS"
           Typeless "abs" or "fabs", etc.  (The usage below indicates it is
           for integers, but it works for any type.)  Use instead of these,
           since the C library ones force their argument to be what it is
           expecting, potentially leading to disaster.  But also beware that
           this evaluates its argument twice, so no "x++".

            int  PERL_ABS(int x)

       "Perl_acos"
       "Perl_asin"
       "Perl_atan"
       "Perl_atan2"
       "Perl_ceil"
       "Perl_cos"
       "Perl_cosh"
       "Perl_exp"
       "Perl_floor"
       "Perl_fmod"
       "Perl_frexp"
       "Perl_isfinite"
       "Perl_isinf"
       "Perl_isnan"
       "Perl_ldexp"
       "Perl_log"
       "Perl_log10"
       "Perl_modf"
       "Perl_pow"
       "Perl_sin"
       "Perl_sinh"
       "Perl_sqrt"
       "Perl_tan"
       "Perl_tanh"
           These perform the corresponding mathematical operation on the
           operand(s), using the libc function designed for the task that has
           just enough precision for an NV on this platform.  If no such
           function with sufficient precision exists, the highest precision
           one available is used.

            NV  Perl_acos    (NV x)
            NV  Perl_asin    (NV x)
            NV  Perl_atan    (NV x)
            NV  Perl_atan2   (NV x, NV y)
            NV  Perl_ceil    (NV x)
            NV  Perl_cos     (NV x)
            NV  Perl_cosh    (NV x)
            NV  Perl_exp     (NV x)
            NV  Perl_floor   (NV x)
            NV  Perl_fmod    (NV x, NV y)
            NV  Perl_frexp   (NV x, int *exp)
            IV  Perl_isfinite(NV x)
            IV  Perl_isinf   (NV x)
            IV  Perl_isnan   (NV x)
            NV  Perl_ldexp   (NV x, int exp)
            NV  Perl_log     (NV x)
            NV  Perl_log10   (NV x)
            NV  Perl_modf    (NV x, NV *iptr)
            NV  Perl_pow     (NV x, NV y)
            NV  Perl_sin     (NV x)
            NV  Perl_sinh    (NV x)
            NV  Perl_sqrt    (NV x)
            NV  Perl_tan     (NV x)
            NV  Perl_tanh    (NV x)

       "Perl_signbit"
           NOTE: "Perl_signbit" is experimental and may change or be removed
           without notice.

           Return a non-zero integer if the sign bit on an NV is set, and 0 if
           it is not.

           If Configure detects this system has a "signbit()" that will work
           with our NVs, then we just use it via the "#define" in perl.h.
           Otherwise, fall back on this implementation.  The main use of this
           function is catching "-0.0".

           "Configure" notes:  This function is called 'Perl_signbit' instead
           of a plain 'signbit' because it is easy to imagine a system having
           a "signbit()" function or macro that doesn't happen to work with
           our particular choice of NVs.  We shouldn't just re-"#define"
           "signbit" as "Perl_signbit" and expect the standard system headers
           to be happy.  Also, this is a no-context function (no "pTHX_")
           because "Perl_signbit()" is usually re-"#defined" in perl.h as a
           simple macro call to the system's "signbit()".  Users should just
           always call "Perl_signbit()".

            int  Perl_signbit(NV f)

       "PL_hexdigit"
           This array, indexed by an integer, converts that value into the
           character that represents it.  For example, if the input is 8, the
           return will be a string whose first character is '8'.  What is
           actually returned is a pointer into a string.  All you are
           interested in is the first character of that string.  To get
           uppercase letters (for the values 10..15), add 16 to the index.
           Hence, "PL_hexdigit[11]" is 'b', and "PL_hexdigit[11+16]" is 'B'.
           Adding 16 to an index whose representation is '0'..'9' yields the
           same as not adding 16.  Indices outside the range 0..31 result in
           (bad) undedefined behavior.

       "READ_XDIGIT"
           Returns the value of an ASCII-range hex digit and advances the
           string pointer.  Behaviour is only well defined when isXDIGIT(*str)
           is true.

            U8  READ_XDIGIT(char str*)

       "scan_bin"
           For backwards compatibility.  Use "grok_bin" instead.

            NV  scan_bin(const char* start, STRLEN len, STRLEN* retlen)

       "scan_hex"
           For backwards compatibility.  Use "grok_hex" instead.

            NV  scan_hex(const char* start, STRLEN len, STRLEN* retlen)

       "scan_oct"
           For backwards compatibility.  Use "grok_oct" instead.

            NV  scan_oct(const char* start, STRLEN len, STRLEN* retlen)

       "seedDrand01"
           This symbol defines the macro to be used in seeding the random
           number generator (see "Drand01").

            void  seedDrand01(Rand_seed_t x)

       "Strtod"
           This is a synonym for "my_strtod".

            NV  Strtod(NN const char * const s, NULLOK char ** e)

       "Strtol"
           Platform and configuration independent "strtol".  This expands to
           the appropriate "strotol"-like function based on the platform and
           Configure options>.  For example it could expand to "strtoll" or
           "strtoq" instead of "strtol".

            NV  Strtol(NN const char * const s, NULLOK char ** e, int base)

       "Strtoul"
           Platform and configuration independent "strtoul".  This expands to
           the appropriate "strotoul"-like function based on the platform and
           Configure options>.  For example it could expand to "strtoull" or
           "strtouq" instead of "strtoul".

            NV  Strtoul(NN const char * const s, NULLOK char ** e, int base)


Optree construction

       "newASSIGNOP"
           Constructs, checks, and returns an assignment op.  "left" and
           "right" supply the parameters of the assignment; they are consumed
           by this function and become part of the constructed op tree.

           If "optype" is "OP_ANDASSIGN", "OP_ORASSIGN", or "OP_DORASSIGN",
           then a suitable conditional optree is constructed.  If "optype" is
           the opcode of a binary operator, such as "OP_BIT_OR", then an op is
           constructed that performs the binary operation and assigns the
           result to the left argument.  Either way, if "optype" is non-zero
           then "flags" has no effect.

           If "optype" is zero, then a plain scalar or list assignment is
           constructed.  Which type of assignment it is is automatically
           determined.  "flags" gives the eight bits of "op_flags", except
           that "OPf_KIDS" will be set automatically, and, shifted up eight
           bits, the eight bits of "op_private", except that the bit with
           value 1 or 2 is automatically set as required.

            OP*  newASSIGNOP(I32 flags, OP* left, I32 optype, OP* right)

       "newBINOP"
           Constructs, checks, and returns an op of any binary type.  "type"
           is the opcode.  "flags" gives the eight bits of "op_flags", except
           that "OPf_KIDS" will be set automatically, and, shifted up eight
           bits, the eight bits of "op_private", except that the bit with
           value 1 or 2 is automatically set as required.  "first" and "last"
           supply up to two ops to be the direct children of the binary op;
           they are consumed by this function and become part of the
           constructed op tree.

            OP*  newBINOP(I32 type, I32 flags, OP* first, OP* last)

       "newCONDOP"
           Constructs, checks, and returns a conditional-expression
           ("cond_expr") op.  "flags" gives the eight bits of "op_flags",
           except that "OPf_KIDS" will be set automatically, and, shifted up
           eight bits, the eight bits of "op_private", except that the bit
           with value 1 is automatically set.  "first" supplies the expression
           selecting between the two branches, and "trueop" and "falseop"
           supply the branches; they are consumed by this function and become
           part of the constructed op tree.

            OP*  newCONDOP(I32 flags, OP* first, OP* trueop, OP* falseop)

       "newDEFSVOP"
           Constructs and returns an op to access $_.

            OP*  newDEFSVOP()

       "newFOROP"
           Constructs, checks, and returns an op tree expressing a "foreach"
           loop (iteration through a list of values).  This is a heavyweight
           loop, with structure that allows exiting the loop by "last" and
           suchlike.

           "sv" optionally supplies the variable that will be aliased to each
           item in turn; if null, it defaults to $_.  "expr" supplies the list
           of values to iterate over.  "block" supplies the main body of the
           loop, and "cont" optionally supplies a "continue" block that
           operates as a second half of the body.  All of these optree inputs
           are consumed by this function and become part of the constructed op
           tree.

           "flags" gives the eight bits of "op_flags" for the "leaveloop" op
           and, shifted up eight bits, the eight bits of "op_private" for the
           "leaveloop" op, except that (in both cases) some bits will be set
           automatically.

            OP*  newFOROP(I32 flags, OP* sv, OP* expr, OP* block, OP* cont)

       "newGIVENOP"
           Constructs, checks, and returns an op tree expressing a "given"
           block.  "cond" supplies the expression to whose value $_ will be
           locally aliased, and "block" supplies the body of the "given"
           construct; they are consumed by this function and become part of
           the constructed op tree.  "defsv_off" must be zero (it used to
           identity the pad slot of lexical $_).

            OP*  newGIVENOP(OP* cond, OP* block, PADOFFSET defsv_off)

       "newGVOP"
           Constructs, checks, and returns an op of any type that involves an
           embedded reference to a GV.  "type" is the opcode.  "flags" gives
           the eight bits of "op_flags".  "gv" identifies the GV that the op
           should reference; calling this function does not transfer ownership
           of any reference to it.

            OP*  newGVOP(I32 type, I32 flags, GV* gv)

       "newLISTOP"
           Constructs, checks, and returns an op of any list type.  "type" is
           the opcode.  "flags" gives the eight bits of "op_flags", except
           that "OPf_KIDS" will be set automatically if required.  "first" and
           "last" supply up to two ops to be direct children of the list op;
           they are consumed by this function and become part of the
           constructed op tree.

           For most list operators, the check function expects all the kid ops
           to be present already, so calling "newLISTOP(OP_JOIN, ...)" (e.g.)
           is not appropriate.  What you want to do in that case is create an
           op of type "OP_LIST", append more children to it, and then call
           "op_convert_list".  See "op_convert_list" for more information.

            OP*  newLISTOP(I32 type, I32 flags, OP* first, OP* last)

       "newLOGOP"
           Constructs, checks, and returns a logical (flow control) op.
           "type" is the opcode.  "flags" gives the eight bits of "op_flags",
           except that "OPf_KIDS" will be set automatically, and, shifted up
           eight bits, the eight bits of "op_private", except that the bit
           with value 1 is automatically set.  "first" supplies the expression
           controlling the flow, and "other" supplies the side (alternate)
           chain of ops; they are consumed by this function and become part of
           the constructed op tree.

            OP*  newLOGOP(I32 optype, I32 flags, OP *first, OP *other)

       "newLOOPEX"
           Constructs, checks, and returns a loop-exiting op (such as "goto"
           or "last").  "type" is the opcode.  "label" supplies the parameter
           determining the target of the op; it is consumed by this function
           and becomes part of the constructed op tree.

            OP*  newLOOPEX(I32 type, OP* label)

       "newLOOPOP"
           Constructs, checks, and returns an op tree expressing a loop.  This
           is only a loop in the control flow through the op tree; it does not
           have the heavyweight loop structure that allows exiting the loop by
           "last" and suchlike.  "flags" gives the eight bits of "op_flags"
           for the top-level op, except that some bits will be set
           automatically as required.  "expr" supplies the expression
           controlling loop iteration, and "block" supplies the body of the
           loop; they are consumed by this function and become part of the
           constructed op tree.  "debuggable" is currently unused and should
           always be 1.

            OP*  newLOOPOP(I32 flags, I32 debuggable, OP* expr, OP* block)

       "newMETHOP"
           Constructs, checks, and returns an op of method type with a method
           name evaluated at runtime.  "type" is the opcode.  "flags" gives
           the eight bits of "op_flags", except that "OPf_KIDS" will be set
           automatically, and, shifted up eight bits, the eight bits of
           "op_private", except that the bit with value 1 is automatically
           set.  "dynamic_meth" supplies an op which evaluates method name; it
           is consumed by this function and become part of the constructed op
           tree.  Supported optypes: "OP_METHOD".

            OP*  newMETHOP(I32 type, I32 flags, OP* dynamic_meth)

       "newMETHOP_named"
           Constructs, checks, and returns an op of method type with a
           constant method name.  "type" is the opcode.  "flags" gives the
           eight bits of "op_flags", and, shifted up eight bits, the eight
           bits of "op_private".  "const_meth" supplies a constant method
           name; it must be a shared COW string.  Supported optypes:
           "OP_METHOD_NAMED".

            OP*  newMETHOP_named(I32 type, I32 flags, SV* const_meth)

       "newNULLLIST"
           Constructs, checks, and returns a new "stub" op, which represents
           an empty list expression.

            OP*  newNULLLIST()

       "newOP"
           Constructs, checks, and returns an op of any base type (any type
           that has no extra fields).  "type" is the opcode.  "flags" gives
           the eight bits of "op_flags", and, shifted up eight bits, the eight
           bits of "op_private".

            OP*  newOP(I32 optype, I32 flags)

       "newPADOP"
           Constructs, checks, and returns an op of any type that involves a
           reference to a pad element.  "type" is the opcode.  "flags" gives
           the eight bits of "op_flags".  A pad slot is automatically
           allocated, and is populated with "sv"; this function takes
           ownership of one reference to it.

           This function only exists if Perl has been compiled to use
           ithreads.

            OP*  newPADOP(I32 type, I32 flags, SV* sv)

       "newPMOP"
           Constructs, checks, and returns an op of any pattern matching type.
           "type" is the opcode.  "flags" gives the eight bits of "op_flags"
           and, shifted up eight bits, the eight bits of "op_private".

            OP*  newPMOP(I32 type, I32 flags)

       "newPVOP"
           Constructs, checks, and returns an op of any type that involves an
           embedded C-level pointer (PV).  "type" is the opcode.  "flags"
           gives the eight bits of "op_flags".  "pv" supplies the C-level
           pointer.  Depending on the op type, the memory referenced by "pv"
           may be freed when the op is destroyed.  If the op is of a freeing
           type, "pv" must have been allocated using "PerlMemShared_malloc".

            OP*  newPVOP(I32 type, I32 flags, char* pv)

       "newRANGE"
           Constructs and returns a "range" op, with subordinate "flip" and
           "flop" ops.  "flags" gives the eight bits of "op_flags" for the
           "flip" op and, shifted up eight bits, the eight bits of
           "op_private" for both the "flip" and "range" ops, except that the
           bit with value 1 is automatically set.  "left" and "right" supply
           the expressions controlling the endpoints of the range; they are
           consumed by this function and become part of the constructed op
           tree.

            OP*  newRANGE(I32 flags, OP* left, OP* right)

       "newSLICEOP"
           Constructs, checks, and returns an "lslice" (list slice) op.
           "flags" gives the eight bits of "op_flags", except that "OPf_KIDS"
           will be set automatically, and, shifted up eight bits, the eight
           bits of "op_private", except that the bit with value 1 or 2 is
           automatically set as required.  "listval" and "subscript" supply
           the parameters of the slice; they are consumed by this function and
           become part of the constructed op tree.

            OP*  newSLICEOP(I32 flags, OP* subscript, OP* listop)

       "newSTATEOP"
           Constructs a state op (COP).  The state op is normally a
           "nextstate" op, but will be a "dbstate" op if debugging is enabled
           for currently-compiled code.  The state op is populated from
           "PL_curcop" (or "PL_compiling").  If "label" is non-null, it
           supplies the name of a label to attach to the state op; this
           function takes ownership of the memory pointed at by "label", and
           will free it.  "flags" gives the eight bits of "op_flags" for the
           state op.

           If "o" is null, the state op is returned.  Otherwise the state op
           is combined with "o" into a "lineseq" list op, which is returned.
           "o" is consumed by this function and becomes part of the returned
           op tree.

            OP*  newSTATEOP(I32 flags, char* label, OP* o)

       "newSVOP"
           Constructs, checks, and returns an op of any type that involves an
           embedded SV.  "type" is the opcode.  "flags" gives the eight bits
           of "op_flags".  "sv" gives the SV to embed in the op; this function
           takes ownership of one reference to it.

            OP*  newSVOP(I32 type, I32 flags, SV* sv)

       "newTRYCATCHOP"
           NOTE: "newTRYCATCHOP" is experimental and may change or be removed
           without notice.

           Constructs and returns a conditional execution statement that
           implements the "try"/"catch" semantics.  First the op tree in
           "tryblock" is executed, inside a context that traps exceptions.  If
           an exception occurs then the optree in "catchblock" is executed,
           with the trapped exception set into the lexical variable given by
           "catchvar" (which must be an op of type "OP_PADSV").  All the
           optrees are consumed by this function and become part of the
           returned op tree.

           The "flags" argument is currently ignored.

            OP*  newTRYCATCHOP(I32 flags, OP* tryblock, OP *catchvar,
                               OP* catchblock)

       "newUNOP"
           Constructs, checks, and returns an op of any unary type.  "type" is
           the opcode.  "flags" gives the eight bits of "op_flags", except
           that "OPf_KIDS" will be set automatically if required, and, shifted
           up eight bits, the eight bits of "op_private", except that the bit
           with value 1 is automatically set.  "first" supplies an optional op
           to be the direct child of the unary op; it is consumed by this
           function and become part of the constructed op tree.

            OP*  newUNOP(I32 type, I32 flags, OP* first)

       "newUNOP_AUX"
           Similar to "newUNOP", but creates an "UNOP_AUX" struct instead,
           with "op_aux" initialised to "aux"

            OP*  newUNOP_AUX(I32 type, I32 flags, OP* first,
                             UNOP_AUX_item *aux)

       "newWHENOP"
           Constructs, checks, and returns an op tree expressing a "when"
           block.  "cond" supplies the test expression, and "block" supplies
           the block that will be executed if the test evaluates to true; they
           are consumed by this function and become part of the constructed op
           tree.  "cond" will be interpreted DWIMically, often as a comparison
           against $_, and may be null to generate a "default" block.

            OP*  newWHENOP(OP* cond, OP* block)

       "newWHILEOP"
           Constructs, checks, and returns an op tree expressing a "while"
           loop.  This is a heavyweight loop, with structure that allows
           exiting the loop by "last" and suchlike.

           "loop" is an optional preconstructed "enterloop" op to use in the
           loop; if it is null then a suitable op will be constructed
           automatically.  "expr" supplies the loop's controlling expression.
           "block" supplies the main body of the loop, and "cont" optionally
           supplies a "continue" block that operates as a second half of the
           body.  All of these optree inputs are consumed by this function and
           become part of the constructed op tree.

           "flags" gives the eight bits of "op_flags" for the "leaveloop" op
           and, shifted up eight bits, the eight bits of "op_private" for the
           "leaveloop" op, except that (in both cases) some bits will be set
           automatically.  "debuggable" is currently unused and should always
           be 1.  "has_my" can be supplied as true to force the loop body to
           be enclosed in its own scope.

            OP*  newWHILEOP(I32 flags, I32 debuggable, LOOP* loop, OP* expr,
                            OP* block, OP* cont, I32 has_my)

       "PL_opfreehook"
           When non-"NULL", the function pointed by this variable will be
           called each time an OP is freed with the corresponding OP as the
           argument.  This allows extensions to free any extra attribute they
           have locally attached to an OP.  It is also assured to first fire
           for the parent OP and then for its kids.

           When you replace this variable, it is considered a good practice to
           store the possibly previously installed hook and that you recall it
           inside your own.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            Perl_ophook_t  PL_opfreehook

       "PL_peepp"
           Pointer to the per-subroutine peephole optimiser.  This is a
           function that gets called at the end of compilation of a Perl
           subroutine (or equivalently independent piece of Perl code) to
           perform fixups of some ops and to perform small-scale
           optimisations.  The function is called once for each subroutine
           that is compiled, and is passed, as sole parameter, a pointer to
           the op that is the entry point to the subroutine.  It modifies the
           op tree in place.

           The peephole optimiser should never be completely replaced.
           Rather, add code to it by wrapping the existing optimiser.  The
           basic way to do this can be seen in "Compile pass 3: peephole
           optimization" in perlguts.  If the new code wishes to operate on
           ops throughout the subroutine's structure, rather than just at the
           top level, it is likely to be more convenient to wrap the
           "PL_rpeepp" hook.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            peep_t  PL_peepp

       "PL_rpeepp"
           Pointer to the recursive peephole optimiser.  This is a function
           that gets called at the end of compilation of a Perl subroutine (or
           equivalently independent piece of Perl code) to perform fixups of
           some ops and to perform small-scale optimisations.  The function is
           called once for each chain of ops linked through their "op_next"
           fields; it is recursively called to handle each side chain.  It is
           passed, as sole parameter, a pointer to the op that is at the head
           of the chain.  It modifies the op tree in place.

           The peephole optimiser should never be completely replaced.
           Rather, add code to it by wrapping the existing optimiser.  The
           basic way to do this can be seen in "Compile pass 3: peephole
           optimization" in perlguts.  If the new code wishes to operate only
           on ops at a subroutine's top level, rather than throughout the
           structure, it is likely to be more convenient to wrap the
           "PL_peepp" hook.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            peep_t  PL_rpeepp


Optree Manipulation Functions

       "alloccopstash"
           NOTE: "alloccopstash" is experimental and may change or be removed
           without notice.

           Available only under threaded builds, this function allocates an
           entry in "PL_stashpad" for the stash passed to it.

            PADOFFSET  alloccopstash(HV *hv)

       "block_end"
           Handles compile-time scope exit.  "floor" is the savestack index
           returned by "block_start", and "seq" is the body of the block.
           Returns the block, possibly modified.

            OP*  block_end(I32 floor, OP* seq)

       "block_start"
           Handles compile-time scope entry.  Arranges for hints to be
           restored on block exit and also handles pad sequence numbers to
           make lexical variables scope right.  Returns a savestack index for
           use with "block_end".

            int  block_start(int full)

       "ck_entersub_args_list"
           Performs the default fixup of the arguments part of an "entersub"
           op tree.  This consists of applying list context to each of the
           argument ops.  This is the standard treatment used on a call marked
           with "&", or a method call, or a call through a subroutine
           reference, or any other call where the callee can't be identified
           at compile time, or a call where the callee has no prototype.

            OP*  ck_entersub_args_list(OP *entersubop)

       "ck_entersub_args_proto"
           Performs the fixup of the arguments part of an "entersub" op tree
           based on a subroutine prototype.  This makes various modifications
           to the argument ops, from applying context up to inserting "refgen"
           ops, and checking the number and syntactic types of arguments, as
           directed by the prototype.  This is the standard treatment used on
           a subroutine call, not marked with "&", where the callee can be
           identified at compile time and has a prototype.

           "protosv" supplies the subroutine prototype to be applied to the
           call.  It may be a normal defined scalar, of which the string value
           will be used.  Alternatively, for convenience, it may be a
           subroutine object (a "CV*" that has been cast to "SV*") which has a
           prototype.  The prototype supplied, in whichever form, does not
           need to match the actual callee referenced by the op tree.

           If the argument ops disagree with the prototype, for example by
           having an unacceptable number of arguments, a valid op tree is
           returned anyway.  The error is reflected in the parser state,
           normally resulting in a single exception at the top level of
           parsing which covers all the compilation errors that occurred.  In
           the error message, the callee is referred to by the name defined by
           the "namegv" parameter.

            OP*  ck_entersub_args_proto(OP *entersubop, GV *namegv,
                                        SV *protosv)

       "ck_entersub_args_proto_or_list"
           Performs the fixup of the arguments part of an "entersub" op tree
           either based on a subroutine prototype or using default list-
           context processing.  This is the standard treatment used on a
           subroutine call, not marked with "&", where the callee can be
           identified at compile time.

           "protosv" supplies the subroutine prototype to be applied to the
           call, or indicates that there is no prototype.  It may be a normal
           scalar, in which case if it is defined then the string value will
           be used as a prototype, and if it is undefined then there is no
           prototype.  Alternatively, for convenience, it may be a subroutine
           object (a "CV*" that has been cast to "SV*"), of which the
           prototype will be used if it has one.  The prototype (or lack
           thereof) supplied, in whichever form, does not need to match the
           actual callee referenced by the op tree.

           If the argument ops disagree with the prototype, for example by
           having an unacceptable number of arguments, a valid op tree is
           returned anyway.  The error is reflected in the parser state,
           normally resulting in a single exception at the top level of
           parsing which covers all the compilation errors that occurred.  In
           the error message, the callee is referred to by the name defined by
           the "namegv" parameter.

            OP*  ck_entersub_args_proto_or_list(OP *entersubop, GV *namegv,
                                                SV *protosv)

       "cv_const_sv"
           If "cv" is a constant sub eligible for inlining, returns the
           constant value returned by the sub.  Otherwise, returns "NULL".

           Constant subs can be created with "newCONSTSUB" or as described in
           "Constant Functions" in perlsub.

            SV*  cv_const_sv(const CV *const cv)

       "cv_get_call_checker"
           The original form of "cv_get_call_checker_flags", which does not
           return checker flags.  When using a checker function returned by
           this function, it is only safe to call it with a genuine GV as its
           "namegv" argument.

            void  cv_get_call_checker(CV *cv, Perl_call_checker *ckfun_p,
                                      SV **ckobj_p)

       "cv_get_call_checker_flags"
           Retrieves the function that will be used to fix up a call to "cv".
           Specifically, the function is applied to an "entersub" op tree for
           a subroutine call, not marked with "&", where the callee can be
           identified at compile time as "cv".

           The C-level function pointer is returned in *ckfun_p, an SV
           argument for it is returned in *ckobj_p, and control flags are
           returned in *ckflags_p.  The function is intended to be called in
           this manner:

            entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));

           In this call, "entersubop" is a pointer to the "entersub" op, which
           may be replaced by the check function, and "namegv" supplies the
           name that should be used by the check function to refer to the
           callee of the "entersub" op if it needs to emit any diagnostics.
           It is permitted to apply the check function in non-standard
           situations, such as to a call to a different subroutine or to a
           method call.

           "namegv" may not actually be a GV.  If the
           "CALL_CHECKER_REQUIRE_GV" bit is clear in *ckflags_p, it is
           permitted to pass a CV or other SV instead, anything that can be
           used as the first argument to "cv_name".  If the
           "CALL_CHECKER_REQUIRE_GV" bit is set in *ckflags_p then the check
           function requires "namegv" to be a genuine GV.

           By default, the check function is
           Perl_ck_entersub_args_proto_or_list, the SV parameter is "cv"
           itself, and the "CALL_CHECKER_REQUIRE_GV" flag is clear.  This
           implements standard prototype processing.  It can be changed, for a
           particular subroutine, by "cv_set_call_checker_flags".

           If the "CALL_CHECKER_REQUIRE_GV" bit is set in "gflags" then it
           indicates that the caller only knows about the genuine GV version
           of "namegv", and accordingly the corresponding bit will always be
           set in *ckflags_p, regardless of the check function's recorded
           requirements.  If the "CALL_CHECKER_REQUIRE_GV" bit is clear in
           "gflags" then it indicates the caller knows about the possibility
           of passing something other than a GV as "namegv", and accordingly
           the corresponding bit may be either set or clear in *ckflags_p,
           indicating the check function's recorded requirements.

           "gflags" is a bitset passed into "cv_get_call_checker_flags", in
           which only the "CALL_CHECKER_REQUIRE_GV" bit currently has a
           defined meaning (for which see above).  All other bits should be
           clear.

            void  cv_get_call_checker_flags(CV *cv, U32 gflags,
                                            Perl_call_checker *ckfun_p,
                                            SV **ckobj_p, U32 *ckflags_p)

       "cv_set_call_checker"
           The original form of "cv_set_call_checker_flags", which passes it
           the "CALL_CHECKER_REQUIRE_GV" flag for backward-compatibility.  The
           effect of that flag setting is that the check function is
           guaranteed to get a genuine GV as its "namegv" argument.

            void  cv_set_call_checker(CV *cv, Perl_call_checker ckfun,
                                      SV *ckobj)

       "cv_set_call_checker_flags"
           Sets the function that will be used to fix up a call to "cv".
           Specifically, the function is applied to an "entersub" op tree for
           a subroutine call, not marked with "&", where the callee can be
           identified at compile time as "cv".

           The C-level function pointer is supplied in "ckfun", an SV argument
           for it is supplied in "ckobj", and control flags are supplied in
           "ckflags".  The function should be defined like this:

               STATIC OP * ckfun(pTHX_ OP *op, GV *namegv, SV *ckobj)

           It is intended to be called in this manner:

               entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);

           In this call, "entersubop" is a pointer to the "entersub" op, which
           may be replaced by the check function, and "namegv" supplies the
           name that should be used by the check function to refer to the
           callee of the "entersub" op if it needs to emit any diagnostics.
           It is permitted to apply the check function in non-standard
           situations, such as to a call to a different subroutine or to a
           method call.

           "namegv" may not actually be a GV.  For efficiency, perl may pass a
           CV or other SV instead.  Whatever is passed can be used as the
           first argument to "cv_name".  You can force perl to pass a GV by
           including "CALL_CHECKER_REQUIRE_GV" in the "ckflags".

           "ckflags" is a bitset, in which only the "CALL_CHECKER_REQUIRE_GV"
           bit currently has a defined meaning (for which see above).  All
           other bits should be clear.

           The current setting for a particular CV can be retrieved by
           "cv_get_call_checker_flags".

            void  cv_set_call_checker_flags(CV *cv, Perl_call_checker ckfun,
                                            SV *ckobj, U32 ckflags)

       "LINKLIST"
           Given the root of an optree, link the tree in execution order using
           the "op_next" pointers and return the first op executed.  If this
           has already been done, it will not be redone, and "o->op_next" will
           be returned.  If "o->op_next" is not already set, "o" should be at
           least an "UNOP".

            OP*  LINKLIST(OP *o)

       "newATTRSUB"
           Construct a Perl subroutine, also performing some surrounding jobs.

           This is the same as ""newATTRSUB_x"" in perlintern with its
           "o_is_gv" parameter set to FALSE.  This means that if "o" is null,
           the new sub will be anonymous; otherwise the name will be derived
           from "o" in the way described (as with all other details) in
           ""newATTRSUB_x"" in perlintern.

            CV*  newATTRSUB(I32 floor, OP *o, OP *proto, OP *attrs, OP *block)

       "newCONSTSUB"
           Behaves like "newCONSTSUB_flags", except that "name" is nul-
           terminated rather than of counted length, and no flags are set.
           (This means that "name" is always interpreted as Latin-1.)

            CV*  newCONSTSUB(HV* stash, const char* name, SV* sv)

       "newCONSTSUB_flags"
           Construct a constant subroutine, also performing some surrounding
           jobs.  A scalar constant-valued subroutine is eligible for inlining
           at compile-time, and in Perl code can be created by
           "sub FOO () { 123 }".  Other kinds of constant subroutine have
           other treatment.

           The subroutine will have an empty prototype and will ignore any
           arguments when called.  Its constant behaviour is determined by
           "sv".  If "sv" is null, the subroutine will yield an empty list.
           If "sv" points to a scalar, the subroutine will always yield that
           scalar.  If "sv" points to an array, the subroutine will always
           yield a list of the elements of that array in list context, or the
           number of elements in the array in scalar context.  This function
           takes ownership of one counted reference to the scalar or array,
           and will arrange for the object to live as long as the subroutine
           does.  If "sv" points to a scalar then the inlining assumes that
           the value of the scalar will never change, so the caller must
           ensure that the scalar is not subsequently written to.  If "sv"
           points to an array then no such assumption is made, so it is
           ostensibly safe to mutate the array or its elements, but whether
           this is really supported has not been determined.

           The subroutine will have "CvFILE" set according to "PL_curcop".
           Other aspects of the subroutine will be left in their default
           state.  The caller is free to mutate the subroutine beyond its
           initial state after this function has returned.

           If "name" is null then the subroutine will be anonymous, with its
           "CvGV" referring to an "__ANON__" glob.  If "name" is non-null then
           the subroutine will be named accordingly, referenced by the
           appropriate glob.  "name" is a string of length "len" bytes giving
           a sigilless symbol name, in UTF-8 if "flags" has the "SVf_UTF8" bit
           set and in Latin-1 otherwise.  The name may be either qualified or
           unqualified.  If the name is unqualified then it defaults to being
           in the stash specified by "stash" if that is non-null, or to
           "PL_curstash" if "stash" is null.  The symbol is always added to
           the stash if necessary, with "GV_ADDMULTI" semantics.

           "flags" should not have bits set other than "SVf_UTF8".

           If there is already a subroutine of the specified name, then the
           new sub will replace the existing one in the glob.  A warning may
           be generated about the redefinition.

           If the subroutine has one of a few special names, such as "BEGIN"
           or "END", then it will be claimed by the appropriate queue for
           automatic running of phase-related subroutines.  In this case the
           relevant glob will be left not containing any subroutine, even if
           it did contain one before.  Execution of the subroutine will likely
           be a no-op, unless "sv" was a tied array or the caller modified the
           subroutine in some interesting way before it was executed.  In the
           case of "BEGIN", the treatment is buggy: the sub will be executed
           when only half built, and may be deleted prematurely, possibly
           causing a crash.

           The function returns a pointer to the constructed subroutine.  If
           the sub is anonymous then ownership of one counted reference to the
           subroutine is transferred to the caller.  If the sub is named then
           the caller does not get ownership of a reference.  In most such
           cases, where the sub has a non-phase name, the sub will be alive at
           the point it is returned by virtue of being contained in the glob
           that names it.  A phase-named subroutine will usually be alive by
           virtue of the reference owned by the phase's automatic run queue.
           A "BEGIN" subroutine may have been destroyed already by the time
           this function returns, but currently bugs occur in that case before
           the caller gets control.  It is the caller's responsibility to
           ensure that it knows which of these situations applies.

            CV*  newCONSTSUB_flags(HV* stash, const char* name, STRLEN len,
                                   U32 flags, SV* sv)

       "newSUB"
           Like "newATTRSUB", but without attributes.

            CV*  newSUB(I32 floor, OP* o, OP* proto, OP* block)

       "newXS"
           Used by "xsubpp" to hook up XSUBs as Perl subs.  "filename" needs
           to be static storage, as it is used directly as CvFILE(), without a
           copy being made.

       "op_append_elem"
           Append an item to the list of ops contained directly within a list-
           type op, returning the lengthened list.  "first" is the list-type
           op, and "last" is the op to append to the list.  "optype" specifies
           the intended opcode for the list.  If "first" is not already a list
           of the right type, it will be upgraded into one.  If either "first"
           or "last" is null, the other is returned unchanged.

            OP*  op_append_elem(I32 optype, OP* first, OP* last)

       "op_append_list"
           Concatenate the lists of ops contained directly within two list-
           type ops, returning the combined list.  "first" and "last" are the
           list-type ops to concatenate.  "optype" specifies the intended
           opcode for the list.  If either "first" or "last" is not already a
           list of the right type, it will be upgraded into one.  If either
           "first" or "last" is null, the other is returned unchanged.

            OP*  op_append_list(I32 optype, OP* first, OP* last)

       "OP_CLASS"
           Return the class of the provided OP: that is, which of the *OP
           structures it uses.  For core ops this currently gets the
           information out of "PL_opargs", which does not always accurately
           reflect the type used; in v5.26 onwards, see also the function
           "op_class" which can do a better job of determining the used type.

           For custom ops the type is returned from the registration, and it
           is up to the registree to ensure it is accurate.  The value
           returned will be one of the "OA_"* constants from op.h.

            U32  OP_CLASS(OP *o)

       "op_contextualize"
           Applies a syntactic context to an op tree representing an
           expression.  "o" is the op tree, and "context" must be "G_SCALAR",
           "G_ARRAY", or "G_VOID" to specify the context to apply.  The
           modified op tree is returned.

            OP*  op_contextualize(OP* o, I32 context)

       "op_convert_list"
           Converts "o" into a list op if it is not one already, and then
           converts it into the specified "type", calling its check function,
           allocating a target if it needs one, and folding constants.

           A list-type op is usually constructed one kid at a time via
           "newLISTOP", "op_prepend_elem" and "op_append_elem".  Then finally
           it is passed to "op_convert_list" to make it the right type.

            OP*  op_convert_list(I32 optype, I32 flags, OP* o)

       "OP_DESC"
           Return a short description of the provided OP.

            const char *  OP_DESC(OP *o)

       "op_free"
           Free an op and its children. Only use this when an op is no longer
           linked to from any optree.

            void  op_free(OP* arg)

       "OpHAS_SIBLING"
           Returns true if "o" has a sibling

            bool  OpHAS_SIBLING(OP *o)

       "OpLASTSIB_set"
           Marks "o" as having no further siblings and marks o as having the
           specified parent. See also "OpMORESIB_set" and "OpMAYBESIB_set".
           For a higher-level interface, see "op_sibling_splice".

            void  OpLASTSIB_set(OP *o, OP *parent)

       "op_linklist"
           This function is the implementation of the "LINKLIST" macro.  It
           should not be called directly.

            OP*  op_linklist(OP *o)

       "op_lvalue"
           NOTE: "op_lvalue" is experimental and may change or be removed
           without notice.

           Propagate lvalue ("modifiable") context to an op and its children.
           "type" represents the context type, roughly based on the type of op
           that would do the modifying, although "local()" is represented by
           "OP_NULL", because it has no op type of its own (it is signalled by
           a flag on the lvalue op).

           This function detects things that can't be modified, such as
           "$x+1", and generates errors for them.  For example, "$x+1 = 2"
           would cause it to be called with an op of type "OP_ADD" and a
           "type" argument of "OP_SASSIGN".

           It also flags things that need to behave specially in an lvalue
           context, such as "$$x = 5" which might have to vivify a reference
           in $x.

            OP*  op_lvalue(OP* o, I32 type)

       "OpMAYBESIB_set"
           Conditionally does "OpMORESIB_set" or "OpLASTSIB_set" depending on
           whether "sib" is non-null. For a higher-level interface, see
           "op_sibling_splice".

            void  OpMAYBESIB_set(OP *o, OP *sib, OP *parent)

       "OpMORESIB_set"
           Sets the sibling of "o" to the non-zero value "sib". See also
           "OpLASTSIB_set" and "OpMAYBESIB_set". For a higher-level interface,
           see "op_sibling_splice".

            void  OpMORESIB_set(OP *o, OP *sib)

       "OP_NAME"
           Return the name of the provided OP.  For core ops this looks up the
           name from the op_type; for custom ops from the op_ppaddr.

            const char *  OP_NAME(OP *o)

       "op_null"
           Neutralizes an op when it is no longer needed, but is still linked
           to from other ops.

            void  op_null(OP* o)

       "op_parent"
           Returns the parent OP of "o", if it has a parent. Returns "NULL"
           otherwise.

            OP*  op_parent(OP *o)

       "op_prepend_elem"
           Prepend an item to the list of ops contained directly within a
           list-type op, returning the lengthened list.  "first" is the op to
           prepend to the list, and "last" is the list-type op.  "optype"
           specifies the intended opcode for the list.  If "last" is not
           already a list of the right type, it will be upgraded into one.  If
           either "first" or "last" is null, the other is returned unchanged.

            OP*  op_prepend_elem(I32 optype, OP* first, OP* last)

       "op_scope"
           NOTE: "op_scope" is experimental and may change or be removed
           without notice.

           Wraps up an op tree with some additional ops so that at runtime a
           dynamic scope will be created.  The original ops run in the new
           dynamic scope, and then, provided that they exit normally, the
           scope will be unwound.  The additional ops used to create and
           unwind the dynamic scope will normally be an "enter"/"leave" pair,
           but a "scope" op may be used instead if the ops are simple enough
           to not need the full dynamic scope structure.

            OP*  op_scope(OP* o)

       "OpSIBLING"
           Returns the sibling of "o", or "NULL" if there is no sibling

            OP*  OpSIBLING(OP *o)

       "op_sibling_splice"
           A general function for editing the structure of an existing chain
           of op_sibling nodes.  By analogy with the perl-level "splice()"
           function, allows you to delete zero or more sequential nodes,
           replacing them with zero or more different nodes.  Performs the
           necessary op_first/op_last housekeeping on the parent node and
           op_sibling manipulation on the children.  The last deleted node
           will be marked as the last node by updating the
           op_sibling/op_sibparent or op_moresib field as appropriate.

           Note that op_next is not manipulated, and nodes are not freed; that
           is the responsibility of the caller.  It also won't create a new
           list op for an empty list etc; use higher-level functions like
           op_append_elem() for that.

           "parent" is the parent node of the sibling chain. It may passed as
           "NULL" if the splicing doesn't affect the first or last op in the
           chain.

           "start" is the node preceding the first node to be spliced.
           Node(s) following it will be deleted, and ops will be inserted
           after it.  If it is "NULL", the first node onwards is deleted, and
           nodes are inserted at the beginning.

           "del_count" is the number of nodes to delete.  If zero, no nodes
           are deleted.  If -1 or greater than or equal to the number of
           remaining kids, all remaining kids are deleted.

           "insert" is the first of a chain of nodes to be inserted in place
           of the nodes.  If "NULL", no nodes are inserted.

           The head of the chain of deleted ops is returned, or "NULL" if no
           ops were deleted.

           For example:

               action                    before      after         returns
               ------                    -----       -----         -------

                                         P           P
               splice(P, A, 2, X-Y-Z)    |           |             B-C
                                         A-B-C-D     A-X-Y-Z-D

                                         P           P
               splice(P, NULL, 1, X-Y)   |           |             A
                                         A-B-C-D     X-Y-B-C-D

                                         P           P
               splice(P, NULL, 3, NULL)  |           |             A-B-C
                                         A-B-C-D     D

                                         P           P
               splice(P, B, 0, X-Y)      |           |             NULL
                                         A-B-C-D     A-B-X-Y-C-D

           For lower-level direct manipulation of "op_sibparent" and
           "op_moresib", see "OpMORESIB_set", "OpLASTSIB_set",
           "OpMAYBESIB_set".

            OP*  op_sibling_splice(OP *parent, OP *start, int del_count,
                                   OP* insert)

       "OP_TYPE_IS"
           Returns true if the given OP is not a "NULL" pointer and if it is
           of the given type.

           The negation of this macro, "OP_TYPE_ISNT" is also available as
           well as "OP_TYPE_IS_NN" and "OP_TYPE_ISNT_NN" which elide the NULL
           pointer check.

            bool  OP_TYPE_IS(OP *o, Optype type)

       "OP_TYPE_IS_OR_WAS"
           Returns true if the given OP is not a NULL pointer and if it is of
           the given type or used to be before being replaced by an OP of type
           OP_NULL.

           The negation of this macro, "OP_TYPE_ISNT_AND_WASNT" is also
           available as well as "OP_TYPE_IS_OR_WAS_NN" and
           "OP_TYPE_ISNT_AND_WASNT_NN" which elide the "NULL" pointer check.

            bool  OP_TYPE_IS_OR_WAS(OP *o, Optype type)

       "rv2cv_op_cv"
           Examines an op, which is expected to identify a subroutine at
           runtime, and attempts to determine at compile time which subroutine
           it identifies.  This is normally used during Perl compilation to
           determine whether a prototype can be applied to a function call.
           "cvop" is the op being considered, normally an "rv2cv" op.  A
           pointer to the identified subroutine is returned, if it could be
           determined statically, and a null pointer is returned if it was not
           possible to determine statically.

           Currently, the subroutine can be identified statically if the RV
           that the "rv2cv" is to operate on is provided by a suitable "gv" or
           "const" op.  A "gv" op is suitable if the GV's CV slot is
           populated.  A "const" op is suitable if the constant value must be
           an RV pointing to a CV.  Details of this process may change in
           future versions of Perl.  If the "rv2cv" op has the
           "OPpENTERSUB_AMPER" flag set then no attempt is made to identify
           the subroutine statically: this flag is used to suppress compile-
           time magic on a subroutine call, forcing it to use default runtime
           behaviour.

           If "flags" has the bit "RV2CVOPCV_MARK_EARLY" set, then the
           handling of a GV reference is modified.  If a GV was examined and
           its CV slot was found to be empty, then the "gv" op has the
           "OPpEARLY_CV" flag set.  If the op is not optimised away, and the
           CV slot is later populated with a subroutine having a prototype,
           that flag eventually triggers the warning "called too early to
           check prototype".

           If "flags" has the bit "RV2CVOPCV_RETURN_NAME_GV" set, then instead
           of returning a pointer to the subroutine it returns a pointer to
           the GV giving the most appropriate name for the subroutine in this
           context.  Normally this is just the "CvGV" of the subroutine, but
           for an anonymous ("CvANON") subroutine that is referenced through a
           GV it will be the referencing GV.  The resulting "GV*" is cast to
           "CV*" to be returned.  A null pointer is returned as usual if there
           is no statically-determinable subroutine.

            CV*  rv2cv_op_cv(OP *cvop, U32 flags)


Pack and Unpack

       "pack_cat"
           "DEPRECATED!"  It is planned to remove "pack_cat" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           The engine implementing "pack()" Perl function.  Note: parameters
           "next_in_list" and "flags" are not used.  This call should not be
           used; use "packlist" instead.

            void  pack_cat(SV *cat, const char *pat, const char *patend,
                           SV **beglist, SV **endlist, SV ***next_in_list,
                           U32 flags)

       "packlist"
           The engine implementing "pack()" Perl function.

            void  packlist(SV *cat, const char *pat, const char *patend,
                           SV **beglist, SV **endlist)

       "unpack_str"
           "DEPRECATED!"  It is planned to remove "unpack_str" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           The engine implementing "unpack()" Perl function.  Note: parameters
           "strbeg", "new_s" and "ocnt" are not used.  This call should not be
           used, use "unpackstring" instead.

            SSize_t  unpack_str(const char *pat, const char *patend,
                                const char *s, const char *strbeg,
                                const char *strend, char **new_s, I32 ocnt,
                                U32 flags)

       "unpackstring"
           The engine implementing the "unpack()" Perl function.

           Using the template "pat..patend", this function unpacks the string
           "s..strend" into a number of mortal SVs, which it pushes onto the
           perl argument (@_) stack (so you will need to issue a "PUTBACK"
           before and "SPAGAIN" after the call to this function).  It returns
           the number of pushed elements.

           The "strend" and "patend" pointers should point to the byte
           following the last character of each string.

           Although this function returns its values on the perl argument
           stack, it doesn't take any parameters from that stack (and thus in
           particular there's no need to do a "PUSHMARK" before calling it,
           unlike "call_pv" for example).

            SSize_t  unpackstring(const char *pat, const char *patend,
                                  const char *s, const char *strend,
                                  U32 flags)


Pad Data Structures

       "CvPADLIST"
           NOTE: "CvPADLIST" is experimental and may change or be removed
           without notice.

           CV's can have CvPADLIST(cv) set to point to a PADLIST.  This is the
           CV's scratchpad, which stores lexical variables and opcode
           temporary and per-thread values.

           For these purposes "formats" are a kind-of CV; eval""s are too
           (except they're not callable at will and are always thrown away
           after the eval"" is done executing).  Require'd files are simply
           evals without any outer lexical scope.

           XSUBs do not have a "CvPADLIST".  "dXSTARG" fetches values from
           "PL_curpad", but that is really the callers pad (a slot of which is
           allocated by every entersub). Do not get or set "CvPADLIST" if a CV
           is an XSUB (as determined by "CvISXSUB()"), "CvPADLIST" slot is
           reused for a different internal purpose in XSUBs.

           The PADLIST has a C array where pads are stored.

           The 0th entry of the PADLIST is a PADNAMELIST which represents the
           "names" or rather the "static type information" for lexicals.  The
           individual elements of a PADNAMELIST are PADNAMEs.  Future
           refactorings might stop the PADNAMELIST from being stored in the
           PADLIST's array, so don't rely on it.  See "PadlistNAMES".

           The CvDEPTH'th entry of a PADLIST is a PAD (an AV) which is the
           stack frame at that depth of recursion into the CV.  The 0th slot
           of a frame AV is an AV which is @_.  Other entries are storage for
           variables and op targets.

           Iterating over the PADNAMELIST iterates over all possible pad
           items.  Pad slots for targets ("SVs_PADTMP") and GVs end up having
           &PL_padname_undef "names", while slots for constants have
           &PL_padname_const "names" (see "pad_alloc").  That
           &PL_padname_undef and &PL_padname_const are used is an
           implementation detail subject to change.  To test for them, use
           "!PadnamePV(name)" and "PadnamePV(name) && !PadnameLEN(name)",
           respectively.

           Only "my"/"our" variable slots get valid names.  The rest are op
           targets/GVs/constants which are statically allocated or resolved at
           compile time.  These don't have names by which they can be looked
           up from Perl code at run time through eval"" the way "my"/"our"
           variables can be.  Since they can't be looked up by "name" but only
           by their index allocated at compile time (which is usually in
           "PL_op->op_targ"), wasting a name SV for them doesn't make sense.

           The pad names in the PADNAMELIST have their PV holding the name of
           the variable.  The "COP_SEQ_RANGE_LOW" and "_HIGH" fields form a
           range (low+1..high inclusive) of cop_seq numbers for which the name
           is valid.  During compilation, these fields may hold the special
           value PERL_PADSEQ_INTRO to indicate various stages:

            COP_SEQ_RANGE_LOW        _HIGH
            -----------------        -----
            PERL_PADSEQ_INTRO            0   variable not yet introduced:
                                             { my ($x
            valid-seq#   PERL_PADSEQ_INTRO   variable in scope:
                                             { my ($x);
            valid-seq#          valid-seq#   compilation of scope complete:
                                             { my ($x); .... }

           When a lexical var hasn't yet been introduced, it already exists
           from the perspective of duplicate declarations, but not for
           variable lookups, e.g.

               my ($x, $x); # '"my" variable $x masks earlier declaration'
               my $x = $x;  # equal to my $x = $::x;

           For typed lexicals "PadnameTYPE" points at the type stash.  For
           "our" lexicals, "PadnameOURSTASH" points at the stash of the
           associated global (so that duplicate "our" declarations in the same
           package can be detected).  "PadnameGEN" is sometimes used to store
           the generation number during compilation.

           If "PadnameOUTER" is set on the pad name, then that slot in the
           frame AV is a REFCNT'ed reference to a lexical from "outside".
           Such entries are sometimes referred to as 'fake'.  In this case,
           the name does not use 'low' and 'high' to store a cop_seq range,
           since it is in scope throughout.  Instead 'high' stores some flags
           containing info about the real lexical (is it declared in an anon,
           and is it capable of being instantiated multiple times?), and for
           fake ANONs, 'low' contains the index within the parent's pad where
           the lexical's value is stored, to make cloning quicker.

           If the 'name' is "&" the corresponding entry in the PAD is a CV
           representing a possible closure.

           Note that formats are treated as anon subs, and are cloned each
           time write is called (if necessary).

           The flag "SVs_PADSTALE" is cleared on lexicals each time the "my()"
           is executed, and set on scope exit.  This allows the "Variable $x
           is not available" warning to be generated in evals, such as

               { my $x = 1; sub f { eval '$x'} } f();

           For state vars, "SVs_PADSTALE" is overloaded to mean 'not yet
           initialised', but this internal state is stored in a separate pad
           entry.

            PADLIST *  CvPADLIST(CV *cv)

       "pad_add_name_pvs"
           Exactly like "pad_add_name_pvn", but takes a literal string instead
           of a string/length pair.

            PADOFFSET  pad_add_name_pvs("name", U32 flags, HV *typestash,
                                        HV *ourstash)

       "PadARRAY"
           NOTE: "PadARRAY" is experimental and may change or be removed
           without notice.

           The C array of pad entries.

            SV **  PadARRAY(PAD * pad)

       "pad_findmy_pvs"
           Exactly like "pad_findmy_pvn", but takes a literal string instead
           of a string/length pair.

            PADOFFSET  pad_findmy_pvs("name", U32 flags)

       "PadlistARRAY"
           NOTE: "PadlistARRAY" is experimental and may change or be removed
           without notice.

           The C array of a padlist, containing the pads.  Only subscript it
           with numbers >= 1, as the 0th entry is not guaranteed to remain
           usable.

            PAD **  PadlistARRAY(PADLIST * padlist)

       "PadlistMAX"
           NOTE: "PadlistMAX" is experimental and may change or be removed
           without notice.

           The index of the last allocated space in the padlist.  Note that
           the last pad may be in an earlier slot.  Any entries following it
           will be "NULL" in that case.

            SSize_t  PadlistMAX(PADLIST * padlist)

       "PadlistNAMES"
           NOTE: "PadlistNAMES" is experimental and may change or be removed
           without notice.

           The names associated with pad entries.

            PADNAMELIST *  PadlistNAMES(PADLIST * padlist)

       "PadlistNAMESARRAY"
           NOTE: "PadlistNAMESARRAY" is experimental and may change or be
           removed without notice.

           The C array of pad names.

            PADNAME **  PadlistNAMESARRAY(PADLIST * padlist)

       "PadlistNAMESMAX"
           NOTE: "PadlistNAMESMAX" is experimental and may change or be
           removed without notice.

           The index of the last pad name.

            SSize_t  PadlistNAMESMAX(PADLIST * padlist)

       "PadlistREFCNT"
           NOTE: "PadlistREFCNT" is experimental and may change or be removed
           without notice.

           The reference count of the padlist.  Currently this is always 1.

            U32  PadlistREFCNT(PADLIST * padlist)

       "PadMAX"
           NOTE: "PadMAX" is experimental and may change or be removed without
           notice.

           The index of the last pad entry.

            SSize_t  PadMAX(PAD * pad)

       "PadnameLEN"
           NOTE: "PadnameLEN" is experimental and may change or be removed
           without notice.

           The length of the name.

            STRLEN  PadnameLEN(PADNAME * pn)

       "PadnamelistARRAY"
           NOTE: "PadnamelistARRAY" is experimental and may change or be
           removed without notice.

           The C array of pad names.

            PADNAME **  PadnamelistARRAY(PADNAMELIST * pnl)

       "PadnamelistMAX"
           NOTE: "PadnamelistMAX" is experimental and may change or be removed
           without notice.

           The index of the last pad name.

            SSize_t  PadnamelistMAX(PADNAMELIST * pnl)

       "PadnamelistREFCNT"
           NOTE: "PadnamelistREFCNT" is experimental and may change or be
           removed without notice.

           The reference count of the pad name list.

            SSize_t  PadnamelistREFCNT(PADNAMELIST * pnl)

       "PadnamelistREFCNT_dec"
           NOTE: "PadnamelistREFCNT_dec" is experimental and may change or be
           removed without notice.

           Lowers the reference count of the pad name list.

            void  PadnamelistREFCNT_dec(PADNAMELIST * pnl)

       "PadnamePV"
           NOTE: "PadnamePV" is experimental and may change or be removed
           without notice.

           The name stored in the pad name struct.  This returns "NULL" for a
           target slot.

            char *  PadnamePV(PADNAME * pn)

       "PadnameREFCNT"
           NOTE: "PadnameREFCNT" is experimental and may change or be removed
           without notice.

           The reference count of the pad name.

            SSize_t  PadnameREFCNT(PADNAME * pn)

       "PadnameREFCNT_dec"
           NOTE: "PadnameREFCNT_dec" is experimental and may change or be
           removed without notice.

           Lowers the reference count of the pad name.

            void  PadnameREFCNT_dec(PADNAME * pn)

       "PadnameSV"
           NOTE: "PadnameSV" is experimental and may change or be removed
           without notice.

           Returns the pad name as a mortal SV.

            SV *  PadnameSV(PADNAME * pn)

       "PadnameUTF8"
           NOTE: "PadnameUTF8" is experimental and may change or be removed
           without notice.

           Whether PadnamePV is in UTF-8.  Currently, this is always true.

            bool  PadnameUTF8(PADNAME * pn)

       "pad_new"
           Create a new padlist, updating the global variables for the
           currently-compiling padlist to point to the new padlist.  The
           following flags can be OR'ed together:

               padnew_CLONE        this pad is for a cloned CV
               padnew_SAVE         save old globals on the save stack
               padnew_SAVESUB      also save extra stuff for start of sub

            PADLIST*  pad_new(int flags)

       "PL_comppad"
           NOTE: "PL_comppad" is experimental and may change or be removed
           without notice.

           During compilation, this points to the array containing the values
           part of the pad for the currently-compiling code.  (At runtime a CV
           may have many such value arrays; at compile time just one is
           constructed.)  At runtime, this points to the array containing the
           currently-relevant values for the pad for the currently-executing
           code.

       "PL_comppad_name"
           NOTE: "PL_comppad_name" is experimental and may change or be
           removed without notice.

           During compilation, this points to the array containing the names
           part of the pad for the currently-compiling code.

       "PL_curpad"
           NOTE: "PL_curpad" is experimental and may change or be removed
           without notice.

           Points directly to the body of the "PL_comppad" array.  (I.e., this
           is "PadARRAY(PL_comppad)".)


Password and Group access

       "GRPASSWD"
           This symbol, if defined, indicates to the C program that "struct
           group" in grp.h contains "gr_passwd".

       "HAS_ENDGRENT"
           This symbol, if defined, indicates that the getgrent routine is
           available for finalizing sequential access of the group database.

       "HAS_ENDGRENT_R"
           This symbol, if defined, indicates that the "endgrent_r" routine is
           available to endgrent re-entrantly.

       "HAS_ENDPWENT"
           This symbol, if defined, indicates that the getgrent routine is
           available for finalizing sequential access of the passwd database.

       "HAS_ENDPWENT_R"
           This symbol, if defined, indicates that the "endpwent_r" routine is
           available to endpwent re-entrantly.

       "HAS_GETGRENT"
           This symbol, if defined, indicates that the "getgrent" routine is
           available for sequential access of the group database.

       "HAS_GETGRENT_R"
           This symbol, if defined, indicates that the "getgrent_r" routine is
           available to getgrent re-entrantly.

       "HAS_GETPWENT"
           This symbol, if defined, indicates that the "getpwent" routine is
           available for sequential access of the passwd database.  If this is
           not available, the older "getpw()" function may be available.

       "HAS_GETPWENT_R"
           This symbol, if defined, indicates that the "getpwent_r" routine is
           available to getpwent re-entrantly.

       "HAS_SETGRENT"
           This symbol, if defined, indicates that the "setgrent" routine is
           available for initializing sequential access of the group database.

       "HAS_SETGRENT_R"
           This symbol, if defined, indicates that the "setgrent_r" routine is
           available to setgrent re-entrantly.

       "HAS_SETPWENT"
           This symbol, if defined, indicates that the "setpwent" routine is
           available for initializing sequential access of the passwd
           database.

       "HAS_SETPWENT_R"
           This symbol, if defined, indicates that the "setpwent_r" routine is
           available to setpwent re-entrantly.

       "PWAGE"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_age".

       "PWCHANGE"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_change".

       "PWCLASS"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_class".

       "PWCOMMENT"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_comment".

       "PWEXPIRE"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_expire".

       "PWGECOS"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_gecos".

       "PWPASSWD"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_passwd".

       "PWQUOTA"
           This symbol, if defined, indicates to the C program that "struct
           passwd" contains "pw_quota".


Paths to system commands

       "CSH"
           This symbol, if defined, contains the full pathname of csh.

       "LOC_SED"
           This symbol holds the complete pathname to the sed program.

       "SH_PATH"
           This symbol contains the full pathname to the shell used on this on
           this system to execute Bourne shell scripts.  Usually, this will be
           /bin/sh, though it's possible that some systems will have /bin/ksh,
           /bin/pdksh, /bin/ash, /bin/bash, or even something such as
           D:/bin/sh.exe.


Prototype information

       "CRYPT_R_PROTO"
           This symbol encodes the prototype of "crypt_r".  It is zero if
           "d_crypt_r" is undef, and one of the "REENTRANT_PROTO_T_ABC" macros
           of reentr.h if "d_crypt_r" is defined.

       "CTERMID_R_PROTO"
           This symbol encodes the prototype of "ctermid_r".  It is zero if
           "d_ctermid_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_ctermid_r" is defined.

       "DRAND48_R_PROTO"
           This symbol encodes the prototype of "drand48_r".  It is zero if
           "d_drand48_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_drand48_r" is defined.

       "ENDGRENT_R_PROTO"
           This symbol encodes the prototype of "endgrent_r".  It is zero if
           "d_endgrent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_endgrent_r" is defined.

       "ENDHOSTENT_R_PROTO"
           This symbol encodes the prototype of "endhostent_r".  It is zero if
           "d_endhostent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_endhostent_r" is defined.

       "ENDNETENT_R_PROTO"
           This symbol encodes the prototype of "endnetent_r".  It is zero if
           "d_endnetent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_endnetent_r" is defined.

       "ENDPROTOENT_R_PROTO"
           This symbol encodes the prototype of "endprotoent_r".  It is zero
           if "d_endprotoent_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_endprotoent_r" is
           defined.

       "ENDPWENT_R_PROTO"
           This symbol encodes the prototype of "endpwent_r".  It is zero if
           "d_endpwent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_endpwent_r" is defined.

       "ENDSERVENT_R_PROTO"
           This symbol encodes the prototype of "endservent_r".  It is zero if
           "d_endservent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_endservent_r" is defined.

       "GDBMNDBM_H_USES_PROTOTYPES"
           This symbol, if defined, indicates that gdbm/ndbm.h uses real
           "ANSI" C prototypes instead of K&R style function declarations
           without any parameter information. While "ANSI" C prototypes are
           supported in C++, K&R style function declarations will yield
           errors.

       "GDBM_NDBM_H_USES_PROTOTYPES"
           This symbol, if defined, indicates that <gdbm-ndbm.h> uses real
           "ANSI" C prototypes instead of K&R style function declarations
           without any parameter information. While "ANSI" C prototypes are
           supported in C++, K&R style function declarations will yield
           errors.

       "GETGRENT_R_PROTO"
           This symbol encodes the prototype of "getgrent_r".  It is zero if
           "d_getgrent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getgrent_r" is defined.

       "GETGRGID_R_PROTO"
           This symbol encodes the prototype of "getgrgid_r".  It is zero if
           "d_getgrgid_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getgrgid_r" is defined.

       "GETGRNAM_R_PROTO"
           This symbol encodes the prototype of "getgrnam_r".  It is zero if
           "d_getgrnam_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getgrnam_r" is defined.

       "GETHOSTBYADDR_R_PROTO"
           This symbol encodes the prototype of "gethostbyaddr_r".  It is zero
           if "d_gethostbyaddr_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_gethostbyaddr_r"
           is defined.

       "GETHOSTBYNAME_R_PROTO"
           This symbol encodes the prototype of "gethostbyname_r".  It is zero
           if "d_gethostbyname_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_gethostbyname_r"
           is defined.

       "GETHOSTENT_R_PROTO"
           This symbol encodes the prototype of "gethostent_r".  It is zero if
           "d_gethostent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_gethostent_r" is defined.

       "GETLOGIN_R_PROTO"
           This symbol encodes the prototype of "getlogin_r".  It is zero if
           "d_getlogin_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getlogin_r" is defined.

       "GETNETBYADDR_R_PROTO"
           This symbol encodes the prototype of "getnetbyaddr_r".  It is zero
           if "d_getnetbyaddr_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_getnetbyaddr_r" is
           defined.

       "GETNETBYNAME_R_PROTO"
           This symbol encodes the prototype of "getnetbyname_r".  It is zero
           if "d_getnetbyname_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_getnetbyname_r" is
           defined.

       "GETNETENT_R_PROTO"
           This symbol encodes the prototype of "getnetent_r".  It is zero if
           "d_getnetent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getnetent_r" is defined.

       "GETPROTOBYNAME_R_PROTO"
           This symbol encodes the prototype of "getprotobyname_r".  It is
           zero if "d_getprotobyname_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_getprotobyname_r"
           is defined.

       "GETPROTOBYNUMBER_R_PROTO"
           This symbol encodes the prototype of "getprotobynumber_r".  It is
           zero if "d_getprotobynumber_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if
           "d_getprotobynumber_r" is defined.

       "GETPROTOENT_R_PROTO"
           This symbol encodes the prototype of "getprotoent_r".  It is zero
           if "d_getprotoent_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_getprotoent_r" is
           defined.

       "GETPWENT_R_PROTO"
           This symbol encodes the prototype of "getpwent_r".  It is zero if
           "d_getpwent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getpwent_r" is defined.

       "GETPWNAM_R_PROTO"
           This symbol encodes the prototype of "getpwnam_r".  It is zero if
           "d_getpwnam_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getpwnam_r" is defined.

       "GETPWUID_R_PROTO"
           This symbol encodes the prototype of "getpwuid_r".  It is zero if
           "d_getpwuid_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getpwuid_r" is defined.

       "GETSERVBYNAME_R_PROTO"
           This symbol encodes the prototype of "getservbyname_r".  It is zero
           if "d_getservbyname_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_getservbyname_r"
           is defined.

       "GETSERVBYPORT_R_PROTO"
           This symbol encodes the prototype of "getservbyport_r".  It is zero
           if "d_getservbyport_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_getservbyport_r"
           is defined.

       "GETSERVENT_R_PROTO"
           This symbol encodes the prototype of "getservent_r".  It is zero if
           "d_getservent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getservent_r" is defined.

       "GETSPNAM_R_PROTO"
           This symbol encodes the prototype of "getspnam_r".  It is zero if
           "d_getspnam_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_getspnam_r" is defined.

       "HAS_DBMINIT_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "dbminit()" function.  Otherwise, it is up to the
           program to supply one.  A good guess is

            extern int dbminit(char *);

       "HAS_DRAND48_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "drand48()" function.  Otherwise, it is up to the
           program to supply one.  A good guess is

            extern double drand48(void);

       "HAS_FLOCK_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "flock()" function.  Otherwise, it is up to the
           program to supply one.  A good guess is

            extern int flock(int, int);

       "HAS_GETHOST_PROTOS"
           This symbol, if defined, indicates that netdb.h includes prototypes
           for "gethostent()", "gethostbyname()", and "gethostbyaddr()".
           Otherwise, it is up to the program to guess them.  See netdbtype.U
           (part of metaconfig) for probing for various "Netdb_xxx_t" types.

       "HAS_GETNET_PROTOS"
           This symbol, if defined, indicates that netdb.h includes prototypes
           for "getnetent()", "getnetbyname()", and "getnetbyaddr()".
           Otherwise, it is up to the program to guess them.  See netdbtype.U
           (part of metaconfig) for probing for various "Netdb_xxx_t" types.

       "HAS_GETPROTO_PROTOS"
           This symbol, if defined, indicates that netdb.h includes prototypes
           for "getprotoent()", "getprotobyname()", and "getprotobyaddr()".
           Otherwise, it is up to the program to guess them.  See netdbtype.U
           (part of metaconfig) for probing for various "Netdb_xxx_t" types.

       "HAS_GETSERV_PROTOS"
           This symbol, if defined, indicates that netdb.h includes prototypes
           for "getservent()", "getservbyname()", and "getservbyaddr()".
           Otherwise, it is up to the program to guess them.  See netdbtype.U
           (part of metaconfig) for probing for various "Netdb_xxx_t" types.

       "HAS_MODFL_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "modfl()" function.  Otherwise, it is up to the
           program to supply one.

       "HAS_SBRK_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "sbrk()" function.  Otherwise, it is up to the
           program to supply one.  Good guesses are

            extern void* sbrk(int);
            extern void* sbrk(size_t);

       "HAS_SETRESGID_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "setresgid()" function.  Otherwise, it is up to
           the program to supply one.  Good guesses are

            extern int setresgid(uid_t ruid, uid_t euid, uid_t suid);

       "HAS_SETRESUID_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "setresuid()" function.  Otherwise, it is up to
           the program to supply one.  Good guesses are

            extern int setresuid(uid_t ruid, uid_t euid, uid_t suid);

       "HAS_SHMAT_PROTOTYPE"
           This symbol, if defined, indicates that the sys/shm.h includes a
           prototype for "shmat()".  Otherwise, it is up to the program to
           guess one.  "Shmat_t" "shmat(int, Shmat_t, int)" is a good guess,
           but not always right so it should be emitted by the program only
           when "HAS_SHMAT_PROTOTYPE" is not defined to avoid conflicting
           defs.

       "HAS_SOCKATMARK_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "sockatmark()" function.  Otherwise, it is up to
           the program to supply one.  A good guess is

            extern int sockatmark(int);

       "HAS_SYSCALL_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "syscall()" function.  Otherwise, it is up to the
           program to supply one.  Good guesses are

            extern int syscall(int,  ...);
            extern int syscall(long, ...);

       "HAS_TELLDIR_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "telldir()" function.  Otherwise, it is up to the
           program to supply one.  A good guess is

            extern long telldir(DIR*);

       "NDBM_H_USES_PROTOTYPES"
           This symbol, if defined, indicates that ndbm.h uses real "ANSI" C
           prototypes instead of K&R style function declarations without any
           parameter information. While "ANSI" C prototypes are supported in
           C++, K&R style function declarations will yield errors.

       "RANDOM_R_PROTO"
           This symbol encodes the prototype of "random_r".  It is zero if
           "d_random_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_random_r" is defined.

       "READDIR_R_PROTO"
           This symbol encodes the prototype of "readdir_r".  It is zero if
           "d_readdir_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_readdir_r" is defined.

       "SETGRENT_R_PROTO"
           This symbol encodes the prototype of "setgrent_r".  It is zero if
           "d_setgrent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_setgrent_r" is defined.

       "SETHOSTENT_R_PROTO"
           This symbol encodes the prototype of "sethostent_r".  It is zero if
           "d_sethostent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_sethostent_r" is defined.

       "SETLOCALE_R_PROTO"
           This symbol encodes the prototype of "setlocale_r".  It is zero if
           "d_setlocale_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_setlocale_r" is defined.

       "SETNETENT_R_PROTO"
           This symbol encodes the prototype of "setnetent_r".  It is zero if
           "d_setnetent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_setnetent_r" is defined.

       "SETPROTOENT_R_PROTO"
           This symbol encodes the prototype of "setprotoent_r".  It is zero
           if "d_setprotoent_r" is undef, and one of the
           "REENTRANT_PROTO_T_ABC" macros of reentr.h if "d_setprotoent_r" is
           defined.

       "SETPWENT_R_PROTO"
           This symbol encodes the prototype of "setpwent_r".  It is zero if
           "d_setpwent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_setpwent_r" is defined.

       "SETSERVENT_R_PROTO"
           This symbol encodes the prototype of "setservent_r".  It is zero if
           "d_setservent_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_setservent_r" is defined.

       "SRAND48_R_PROTO"
           This symbol encodes the prototype of "srand48_r".  It is zero if
           "d_srand48_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_srand48_r" is defined.

       "SRANDOM_R_PROTO"
           This symbol encodes the prototype of "srandom_r".  It is zero if
           "d_srandom_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_srandom_r" is defined.

       "STRERROR_R_PROTO"
           This symbol encodes the prototype of "strerror_r".  It is zero if
           "d_strerror_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_strerror_r" is defined.

       "TMPNAM_R_PROTO"
           This symbol encodes the prototype of "tmpnam_r".  It is zero if
           "d_tmpnam_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_tmpnam_r" is defined.

       "TTYNAME_R_PROTO"
           This symbol encodes the prototype of "ttyname_r".  It is zero if
           "d_ttyname_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_ttyname_r" is defined.


REGEXP Functions

       "pregcomp"
           Described in perlreguts.

            REGEXP*  pregcomp(SV * const pattern, const U32 flags)

       "pregexec"
           Described in perlreguts.

            I32  pregexec(REGEXP * const prog, char* stringarg, char* strend,
                          char* strbeg, SSize_t minend, SV* screamer,
                          U32 nosave)

       "re_dup_guts"
           Duplicate a regexp.

           This routine is expected to clone a given regexp structure. It is
           only compiled under USE_ITHREADS.

           After all of the core data stored in struct regexp is duplicated
           the "regexp_engine.dupe" method is used to copy any private data
           stored in the *pprivate pointer. This allows extensions to handle
           any duplication they need to do.

            void  re_dup_guts(const REGEXP *sstr, REGEXP *dstr,
                              CLONE_PARAMS* param)

       "regmatch_info"
           Some basic information about the current match that is created by
           Perl_regexec_flags and then passed to regtry(), regmatch() etc.  It
           is allocated as a local var on the stack, so nothing should be
           stored in it that needs preserving or clearing up on croak().  For
           that, see the aux_info and aux_info_eval members of the
           regmatch_state union.

       "SvRX"
           Convenience macro to get the REGEXP from a SV.  This is
           approximately equivalent to the following snippet:

               if (SvMAGICAL(sv))
                   mg_get(sv);
               if (SvROK(sv))
                   sv = MUTABLE_SV(SvRV(sv));
               if (SvTYPE(sv) == SVt_REGEXP)
                   return (REGEXP*) sv;

           "NULL" will be returned if a REGEXP* is not found.

            REGEXP *  SvRX(SV *sv)

       "SvRXOK"
           Returns a boolean indicating whether the SV (or the one it
           references) is a REGEXP.

           If you want to do something with the REGEXP* later use SvRX instead
           and check for NULL.

            bool  SvRXOK(SV* sv)


Signals

       "HAS_SIGINFO_SI_ADDR"
           This symbol, if defined, indicates that "siginfo_t" has the
           "si_addr" member

       "HAS_SIGINFO_SI_BAND"
           This symbol, if defined, indicates that "siginfo_t" has the
           "si_band" member

       "HAS_SIGINFO_SI_ERRNO"
           This symbol, if defined, indicates that "siginfo_t" has the
           "si_errno" member

       "HAS_SIGINFO_SI_PID"
           This symbol, if defined, indicates that "siginfo_t" has the
           "si_pid" member

       "HAS_SIGINFO_SI_STATUS"
           This symbol, if defined, indicates that "siginfo_t" has the
           "si_status" member

       "HAS_SIGINFO_SI_UID"
           This symbol, if defined, indicates that "siginfo_t" has the
           "si_uid" member

       "HAS_SIGINFO_SI_VALUE"
           This symbol, if defined, indicates that "siginfo_t" has the
           "si_value" member

       "PERL_SIGNALS_UNSAFE_FLAG"
           If this bit in "PL_signals" is set, the system is uing the pre-Perl
           5.8 unsafe signals.  See "PERL_SIGNALS" in perlrun and "Deferred
           Signals (Safe Signals)" in perlipc.

            U32  PERL_SIGNALS_UNSAFE_FLAG

       "rsignal"
           A wrapper for the C library signal(2).  Don't use the latter, as
           the Perl version knows things that interact with the rest of the
           perl interpreter.

            Sighandler_t  rsignal(int i, Sighandler_t t)

       "Sigjmp_buf"
           This is the buffer type to be used with Sigsetjmp and Siglongjmp.

       "Siglongjmp"
           This macro is used in the same way as "siglongjmp()", but will
           invoke traditional "longjmp()" if siglongjmp isn't available.  See
           "HAS_SIGSETJMP".

            void  Siglongjmp(jmp_buf env, int val)

       "SIG_NAME"
           This symbol contains a list of signal names in order of signal
           number. This is intended to be used as a static array
           initialization, like this:

            char *sig_name[] = { SIG_NAME };

           The signals in the list are separated with commas, and each signal
           is surrounded by double quotes. There is no leading "SIG" in the
           signal name, i.e. "SIGQUIT" is known as ""QUIT"".  Gaps in the
           signal numbers (up to "NSIG") are filled in with "NUMnn", etc.,
           where nn is the actual signal number (e.g. "NUM37").  The signal
           number for "sig_name[i]" is stored in "sig_num[i]".  The last
           element is 0 to terminate the list with a "NULL".  This corresponds
           to the 0 at the end of the "sig_name_init" list.  Note that this
           variable is initialized from the "sig_name_init", not from
           "sig_name" (which is unused).

       "SIG_NUM"
           This symbol contains a list of signal numbers, in the same order as
           the "SIG_NAME" list. It is suitable for static array
           initialization, as in:

            int sig_num[] = { SIG_NUM };

           The signals in the list are separated with commas, and the indices
           within that list and the "SIG_NAME" list match, so it's easy to
           compute the signal name from a number or vice versa at the price of
           a small dynamic linear lookup.  Duplicates are allowed, but are
           moved to the end of the list.  The signal number corresponding to
           "sig_name[i]" is "sig_number[i]".  if (i < "NSIG") then
           "sig_number[i]" == i.  The last element is 0, corresponding to the
           0 at the end of the "sig_name_init" list.  Note that this variable
           is initialized from the "sig_num_init", not from "sig_num" (which
           is unused).

       "Sigsetjmp"
           This macro is used in the same way as "sigsetjmp()", but will
           invoke traditional "setjmp()" if sigsetjmp isn't available.  See
           "HAS_SIGSETJMP".

            int  Sigsetjmp(jmp_buf env, int savesigs)

       "SIG_SIZE"
           This variable contains the number of elements of the "SIG_NAME" and
           "SIG_NUM" arrays, excluding the final "NULL" entry.

       "whichsig"
       "whichsig_pv"
       "whichsig_pvn"
       "whichsig_sv"
           These all convert a signal name into its corresponding signal
           number; returning -1 if no corresponding number was found.

           They differ only in the source of the signal name:

           "whichsig_pv" takes the name from the "NUL"-terminated string
           starting at "sig".

           "whichsig" is merely a different spelling, a synonym, of
           "whichsig_pv".

           "whichsig_pvn" takes the name from the string starting at "sig",
           with length "len" bytes.

           "whichsig_sv" takes the name from the PV stored in the SV "sigsv".

            I32  whichsig    (const char* sig)
            I32  whichsig_pv (const char* sig)
            I32  whichsig_pvn(const char* sig, STRLEN len)
            I32  whichsig_sv (SV* sigsv)


Site configuration

       These variables give details as to where various libraries,
       installation destinations, etc., go, as well as what various
       installation options were selected

       "ARCHLIB"
           This variable, if defined, holds the name of the directory in which
           the user wants to put architecture-dependent public library files
           for perl5.  It is most often a local directory such as
           /usr/local/lib.  Programs using this variable must be prepared to
           deal with filename expansion.  If "ARCHLIB" is the same as
           "PRIVLIB", it is not defined, since presumably the program already
           searches "PRIVLIB".

       "ARCHLIB_EXP"
           This symbol contains the ~name expanded version of "ARCHLIB", to be
           used in programs that are not prepared to deal with ~ expansion at
           run-time.

       "ARCHNAME"
           This symbol holds a string representing the architecture name.  It
           may be used to construct an architecture-dependant pathname where
           library files may be held under a private library, for instance.

       "BIN"
           This symbol holds the path of the bin directory where the package
           will be installed. Program must be prepared to deal with ~name
           substitution.

       "BIN_EXP"
           This symbol is the filename expanded version of the "BIN" symbol,
           for programs that do not want to deal with that at run-time.

       "INSTALL_USR_BIN_PERL"
           This symbol, if defined, indicates that Perl is to be installed
           also as /usr/bin/perl.

       "MULTIARCH"
           This symbol, if defined, signifies that the build process will
           produce some binary files that are going to be used in a cross-
           platform environment.  This is the case for example with the NeXT
           "fat" binaries that contain executables for several "CPUs".

       "PERL_INC_VERSION_LIST"
           This variable specifies the list of subdirectories in over which
           perl.c:"incpush()" and lib/lib.pm will automatically search when
           adding directories to @"INC", in a format suitable for a C
           initialization string.  See the "inc_version_list" entry in
           Porting/Glossary for more details.

       "PERL_OTHERLIBDIRS"
           This variable contains a colon-separated set of paths for the perl
           binary to search for additional library files or modules.  These
           directories will be tacked to the end of @"INC".  Perl will
           automatically search below each path for version- and architecture-
           specific directories.  See "PERL_INC_VERSION_LIST" for more
           details.

       "PERL_RELOCATABLE_INC"
           This symbol, if defined, indicates that we'd like to relocate
           entries in @"INC" at run time based on the location of the perl
           binary.

       "PERL_TARGETARCH"
           This symbol, if defined, indicates the target architecture Perl has
           been cross-compiled to.  Undefined if not a cross-compile.

       "PERL_USE_DEVEL"
           This symbol, if defined, indicates that Perl was configured with
           "-Dusedevel", to enable development features.  This should not be
           done for production builds.

       "PERL_VENDORARCH"
           If defined, this symbol contains the name of a private library.
           The library is private in the sense that it needn't be in anyone's
           execution path, but it should be accessible by the world.  It may
           have a ~ on the front.  The standard distribution will put nothing
           in this directory.  Vendors who distribute perl may wish to place
           their own architecture-dependent modules and extensions in this
           directory with

            MakeMaker Makefile.PL INSTALLDIRS=vendor

           or equivalent.  See "INSTALL" for details.

       "PERL_VENDORARCH_EXP"
           This symbol contains the ~name expanded version of
           "PERL_VENDORARCH", to be used in programs that are not prepared to
           deal with ~ expansion at run-time.

       "PERL_VENDORLIB_EXP"
           This symbol contains the ~name expanded version of "VENDORLIB", to
           be used in programs that are not prepared to deal with ~ expansion
           at run-time.

       "PERL_VENDORLIB_STEM"
           This define is "PERL_VENDORLIB_EXP" with any trailing version-
           specific component removed.  The elements in "inc_version_list"
           ("inc_version_list".U (part of metaconfig)) can be tacked onto this
           variable to generate a list of directories to search.

       "PRIVLIB"
           This symbol contains the name of the private library for this
           package.  The library is private in the sense that it needn't be in
           anyone's execution path, but it should be accessible by the world.
           The program should be prepared to do ~ expansion.

       "PRIVLIB_EXP"
           This symbol contains the ~name expanded version of "PRIVLIB", to be
           used in programs that are not prepared to deal with ~ expansion at
           run-time.

       "SITEARCH"
           This symbol contains the name of the private library for this
           package.  The library is private in the sense that it needn't be in
           anyone's execution path, but it should be accessible by the world.
           The program should be prepared to do ~ expansion.  The standard
           distribution will put nothing in this directory.  After perl has
           been installed, users may install their own local architecture-
           dependent modules in this directory with

            MakeMaker Makefile.PL

           or equivalent.  See "INSTALL" for details.

       "SITEARCH_EXP"
           This symbol contains the ~name expanded version of "SITEARCH", to
           be used in programs that are not prepared to deal with ~ expansion
           at run-time.

       "SITELIB"
           This symbol contains the name of the private library for this
           package.  The library is private in the sense that it needn't be in
           anyone's execution path, but it should be accessible by the world.
           The program should be prepared to do ~ expansion.  The standard
           distribution will put nothing in this directory.  After perl has
           been installed, users may install their own local architecture-
           independent modules in this directory with

            MakeMaker Makefile.PL

           or equivalent.  See "INSTALL" for details.

       "SITELIB_EXP"
           This symbol contains the ~name expanded version of "SITELIB", to be
           used in programs that are not prepared to deal with ~ expansion at
           run-time.

       "SITELIB_STEM"
           This define is "SITELIB_EXP" with any trailing version-specific
           component removed.  The elements in "inc_version_list"
           ("inc_version_list".U (part of metaconfig)) can be tacked onto this
           variable to generate a list of directories to search.

       "STARTPERL"
           This variable contains the string to put in front of a perl script
           to make sure (one hopes) that it runs with perl and not some shell.

       "USE_64_BIT_ALL"
           This symbol, if defined, indicates that 64-bit integers should be
           used when available.  If not defined, the native integers will be
           used (be they 32 or 64 bits).  The maximal possible 64-bitness is
           employed: LP64 or "ILP64", meaning that you will be able to use
           more than 2 gigabytes of memory.  This mode is even more binary
           incompatible than "USE_64_BIT_INT". You may not be able to run the
           resulting executable in a 32-bit "CPU" at all or you may need at
           least to reboot your OS to 64-bit mode.

       "USE_64_BIT_INT"
           This symbol, if defined, indicates that 64-bit integers should be
           used when available.  If not defined, the native integers will be
           employed (be they 32 or 64 bits).  The minimal possible 64-bitness
           is used, just enough to get 64-bit integers into Perl.  This may
           mean using for example "long longs", while your memory may still be
           limited to 2 gigabytes.

       "USE_BSD_GETPGRP"
           This symbol, if defined, indicates that getpgrp needs one arguments
           whereas "USG" one needs none.

       "USE_BSD_SETPGRP"
           This symbol, if defined, indicates that setpgrp needs two arguments
           whereas "USG" one needs none.  See also "HAS_SETPGID" for a "POSIX"
           interface.

       "USE_CPLUSPLUS"
           This symbol, if defined, indicates that a C++ compiler was used to
           compiled Perl and will be used to compile extensions.

       "USE_CROSS_COMPILE"
           This symbol, if defined, indicates that Perl is being cross-
           compiled.

       "USE_C_BACKTRACE"
           This symbol, if defined, indicates that Perl should be built with
           support for backtrace.

       "USE_DTRACE"
           This symbol, if defined, indicates that Perl should be built with
           support for DTrace.

       "USE_DYNAMIC_LOADING"
           This symbol, if defined, indicates that dynamic loading of some
           sort is available.

       "USE_FAST_STDIO"
           This symbol, if defined, indicates that Perl should be built to use
           'fast stdio'.  Defaults to define in Perls 5.8 and earlier, to
           undef later.

       "USE_ITHREADS"
           This symbol, if defined, indicates that Perl should be built to use
           the interpreter-based threading implementation.

       "USE_KERN_PROC_PATHNAME"
           This symbol, if defined, indicates that we can use sysctl with
           "KERN_PROC_PATHNAME" to get a full path for the executable, and
           hence convert $^X to an absolute path.

       "USE_LARGE_FILES"
           This symbol, if defined, indicates that large file support should
           be used when available.

       "USE_LONG_DOUBLE"
           This symbol, if defined, indicates that long doubles should be used
           when available.

       "USE_MORE_BITS"
           This symbol, if defined, indicates that 64-bit interfaces and long
           doubles should be used when available.

       "USE_NSGETEXECUTABLEPATH"
           This symbol, if defined, indicates that we can use
           "_NSGetExecutablePath" and realpath to get a full path for the
           executable, and hence convert $^X to an absolute path.

       "USE_PERLIO"
           This symbol, if defined, indicates that the PerlIO abstraction
           should be used throughout.  If not defined, stdio should be used in
           a fully backward compatible manner.

       "USE_QUADMATH"
           This symbol, if defined, indicates that the quadmath library should
           be used when available.

       "USE_REENTRANT_API"
           This symbol, if defined, indicates that Perl should try to use the
           various "_r" versions of library functions.  This is extremely
           experimental.

       "USE_SEMCTL_SEMID_DS"
           This symbol, if defined, indicates that "struct semid_ds" * is used
           for semctl "IPC_STAT".

       "USE_SEMCTL_SEMUN"
           This symbol, if defined, indicates that "union semun" is used for
           semctl "IPC_STAT".

       "USE_SITECUSTOMIZE"
           This symbol, if defined, indicates that sitecustomize should be
           used.

       "USE_SOCKS"
           This symbol, if defined, indicates that Perl should be built to use
           socks.

       "USE_STAT_BLOCKS"
           This symbol is defined if this system has a stat structure
           declaring "st_blksize" and "st_blocks".

       "USE_STDIO_BASE"
           This symbol is defined if the "_base" field (or similar) of the
           stdio "FILE" structure can be used to access the stdio buffer for a
           file handle.  If this is defined, then the "FILE_base(fp)" macro
           will also be defined and should be used to access this field.
           Also, the "FILE_bufsiz(fp)" macro will be defined and should be
           used to determine the number of bytes in the buffer.
           "USE_STDIO_BASE" will never be defined unless "USE_STDIO_PTR" is.

       "USE_STDIO_PTR"
           This symbol is defined if the "_ptr" and "_cnt" fields (or similar)
           of the stdio "FILE" structure can be used to access the stdio
           buffer for a file handle.  If this is defined, then the
           "FILE_ptr(fp)" and "FILE_cnt(fp)" macros will also be defined and
           should be used to access these fields.

       "USE_STRICT_BY_DEFAULT"
           This symbol, if defined, enables additional defaults.  At this time
           it only enables implicit strict by default.

       "USE_THREADS"
           This symbol, if defined, indicates that Perl should be built to use
           threads.  At present, it is a synonym for and "USE_ITHREADS", but
           eventually the source ought to be changed to use this to mean
           "_any_" threading implementation.


Sockets configuration values

       "HAS_SOCKADDR_IN6"
           This symbol, if defined, indicates the availability of "struct
           sockaddr_in6";

       "HAS_SOCKADDR_SA_LEN"
           This symbol, if defined, indicates that the "struct sockaddr"
           structure has a member called "sa_len", indicating the length of
           the structure.

       "HAS_SOCKADDR_STORAGE"
           This symbol, if defined, indicates the availability of "struct
           sockaddr_storage";

       "HAS_SOCKATMARK"
           This symbol, if defined, indicates that the "sockatmark" routine is
           available to test whether a socket is at the out-of-band mark.

       "HAS_SOCKET"
           This symbol, if defined, indicates that the "BSD" "socket"
           interface is supported.

       "HAS_SOCKETPAIR"
           This symbol, if defined, indicates that the "BSD" "socketpair()"
           call is supported.

       "HAS_SOCKS5_INIT"
           This symbol, if defined, indicates that the "socks5_init" routine
           is available to initialize "SOCKS" 5.

       "I_SOCKS"
           This symbol, if defined, indicates that socks.h exists and should
           be included.

            #ifdef I_SOCKS
                #include <socks.h>
            #endif

       "I_SYS_SOCKIO"
           This symbol, if defined, indicates the sys/sockio.h should be
           included to get socket ioctl options, like "SIOCATMARK".

            #ifdef I_SYS_SOCKIO
                #include <sys_sockio.h>
            #endif


Source Filters

       "filter_add"
           Described in perlfilter.

            SV*  filter_add(filter_t funcp, SV* datasv)

       "filter_read"
           Described in perlfilter.

            I32  filter_read(int idx, SV *buf_sv, int maxlen)


Stack Manipulation Macros

       "BHK"
           Described in perlguts.

       "BINOP"
           Described in perlguts.

       "DESTRUCTORFUNC_NOCONTEXT_t"
           Described in perlguts.

       "DESTRUCTORFUNC_t"
           Described in perlguts.

       "dMARK"
           Declare a stack marker variable, "mark", for the XSUB.  See "MARK"
           and "dORIGMARK".

              dMARK;

       "dORIGMARK"
           Saves the original stack mark for the XSUB.  See "ORIGMARK".

              dORIGMARK;

       "dSP"
           Declares a local copy of perl's stack pointer for the XSUB,
           available via the "SP" macro.  See "SP".

              dSP;

       "dTARGET"
           Declare that this function uses "TARG"

              dTARGET;

       "EXTEND"
           Used to extend the argument stack for an XSUB's return values.
           Once used, guarantees that there is room for at least "nitems" to
           be pushed onto the stack.

            void  EXTEND(SP, SSize_t nitems)

       "LISTOP"
           Described in perlguts.

       "LOGOP"
           Described in perlguts.

       "LOOP"
           Described in perlguts.

       "MARK"
           Stack marker variable for the XSUB.  See "dMARK".

       "mPUSHi"
           Push an integer onto the stack.  The stack must have room for this
           element.  Does not use "TARG".  See also "PUSHi", "mXPUSHi" and
           "XPUSHi".

            void  mPUSHi(IV iv)

       "mPUSHn"
           Push a double onto the stack.  The stack must have room for this
           element.  Does not use "TARG".  See also "PUSHn", "mXPUSHn" and
           "XPUSHn".

            void  mPUSHn(NV nv)

       "mPUSHp"
           Push a string onto the stack.  The stack must have room for this
           element.  The "len" indicates the length of the string.  Does not
           use "TARG".  See also "PUSHp", "mXPUSHp" and "XPUSHp".

            void  mPUSHp(char* str, STRLEN len)

       "mPUSHs"
           Push an SV onto the stack and mortalizes the SV.  The stack must
           have room for this element.  Does not use "TARG".  See also "PUSHs"
           and "mXPUSHs".

            void  mPUSHs(SV* sv)

       "mPUSHu"
           Push an unsigned integer onto the stack.  The stack must have room
           for this element.  Does not use "TARG".  See also "PUSHu",
           "mXPUSHu" and "XPUSHu".

            void  mPUSHu(UV uv)

       "mXPUSHi"
           Push an integer onto the stack, extending the stack if necessary.
           Does not use "TARG".  See also "XPUSHi", "mPUSHi" and "PUSHi".

            void  mXPUSHi(IV iv)

       "mXPUSHn"
           Push a double onto the stack, extending the stack if necessary.
           Does not use "TARG".  See also "XPUSHn", "mPUSHn" and "PUSHn".

            void  mXPUSHn(NV nv)

       "mXPUSHp"
           Push a string onto the stack, extending the stack if necessary.
           The "len" indicates the length of the string.  Does not use "TARG".
           See also "XPUSHp", "mPUSHp" and "PUSHp".

            void  mXPUSHp(char* str, STRLEN len)

       "mXPUSHs"
           Push an SV onto the stack, extending the stack if necessary and
           mortalizes the SV.  Does not use "TARG".  See also "XPUSHs" and
           "mPUSHs".

            void  mXPUSHs(SV* sv)

       "mXPUSHu"
           Push an unsigned integer onto the stack, extending the stack if
           necessary.  Does not use "TARG".  See also "XPUSHu", "mPUSHu" and
           "PUSHu".

            void  mXPUSHu(UV uv)

       "newXSproto"
           Used by "xsubpp" to hook up XSUBs as Perl subs.  Adds Perl
           prototypes to the subs.

       "OP"
           Described in perlguts.

       "ORIGMARK"
           The original stack mark for the XSUB.  See "dORIGMARK".

       "peep_t"
           Described in perlguts.

       "PL_runops"
           Described in perlguts.

       "PMOP"
           Described in perlguts.

       "POPi"
           Pops an integer off the stack.

            IV  POPi

       "POPl"
           Pops a long off the stack.

            long  POPl

       "POPn"
           Pops a double off the stack.

            NV  POPn

       "POPp"
           Pops a string off the stack.

            char*  POPp

       "POPpbytex"
           Pops a string off the stack which must consist of bytes i.e.
           characters < 256.

            char*  POPpbytex

       "POPpx"
           Pops a string off the stack.  Identical to POPp.  There are two
           names for historical reasons.

            char*  POPpx

       "POPs"
           Pops an SV off the stack.

            SV*  POPs

       "POPu"
           Pops an unsigned integer off the stack.

            UV  POPu

       "POPul"
           Pops an unsigned long off the stack.

            long  POPul

       "PUSHi"
           Push an integer onto the stack.  The stack must have room for this
           element.  Handles 'set' magic.  Uses "TARG", so "dTARGET" or
           "dXSTARG" should be called to declare it.  Do not call multiple
           "TARG"-oriented macros to return lists from XSUB's - see "mPUSHi"
           instead.  See also "XPUSHi" and "mXPUSHi".

            void  PUSHi(IV iv)

       "PUSHMARK"
           Opening bracket for arguments on a callback.  See "PUTBACK" and
           perlcall.

            void  PUSHMARK(SP)

       "PUSHmortal"
           Push a new mortal SV onto the stack.  The stack must have room for
           this element.  Does not use "TARG".  See also "PUSHs",
           "XPUSHmortal" and "XPUSHs".

            void  PUSHmortal

       "PUSHn"
           Push a double onto the stack.  The stack must have room for this
           element.  Handles 'set' magic.  Uses "TARG", so "dTARGET" or
           "dXSTARG" should be called to declare it.  Do not call multiple
           "TARG"-oriented macros to return lists from XSUB's - see "mPUSHn"
           instead.  See also "XPUSHn" and "mXPUSHn".

            void  PUSHn(NV nv)

       "PUSHp"
           Push a string onto the stack.  The stack must have room for this
           element.  The "len" indicates the length of the string.  Handles
           'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be
           called to declare it.  Do not call multiple "TARG"-oriented macros
           to return lists from XSUB's - see "mPUSHp" instead.  See also
           "XPUSHp" and "mXPUSHp".

            void  PUSHp(char* str, STRLEN len)

       "PUSHs"
           Push an SV onto the stack.  The stack must have room for this
           element.  Does not handle 'set' magic.  Does not use "TARG".  See
           also "PUSHmortal", "XPUSHs", and "XPUSHmortal".

            void  PUSHs(SV* sv)

       "PUSHu"
           Push an unsigned integer onto the stack.  The stack must have room
           for this element.  Handles 'set' magic.  Uses "TARG", so "dTARGET"
           or "dXSTARG" should be called to declare it.  Do not call multiple
           "TARG"-oriented macros to return lists from XSUB's - see "mPUSHu"
           instead.  See also "XPUSHu" and "mXPUSHu".

            void  PUSHu(UV uv)

       "PUTBACK"
           Closing bracket for XSUB arguments.  This is usually handled by
           "xsubpp".  See "PUSHMARK" and perlcall for other uses.

              PUTBACK;

       "save_aptr"
           Described in perlguts.

            void  save_aptr(AV** aptr)

       "save_ary"
           Described in perlguts.

            AV*  save_ary(GV* gv)

       "SAVEBOOL"
           Described in perlguts.

              SAVEBOOL(bool i)

       "SAVEDELETE"
           Described in perlguts.

              SAVEDELETE(HV * hv, char * key, I32 length)

       "SAVEDESTRUCTOR"
           Described in perlguts.

              SAVEDESTRUCTOR(DESTRUCTORFUNC_NOCONTEXT_t f, void *p)

       "SAVEDESTRUCTOR_X"
           Described in perlguts.

              SAVEDESTRUCTOR_X(DESTRUCTORFUNC_t f, void *p)

       "SAVEFREEOP"
           Described in perlguts.

              SAVEFREEOP(OP *op)

       "SAVEFREEPV"
           Described in perlguts.

              SAVEFREEPV(void * p)

       "SAVEFREESV"
           Described in perlguts.

              SAVEFREESV(SV* sv)

       "save_hash"
           Described in perlguts.

            HV*  save_hash(GV* gv)

       "save_hptr"
           Described in perlguts.

            void  save_hptr(HV** hptr)

       "SAVEI8"
           Described in perlguts.

              SAVEI8(I8 i)

       "SAVEI32"
           Described in perlguts.

              SAVEI32(I32 i)

       "SAVEI16"
           Described in perlguts.

              SAVEI16(I16 i)

       "SAVEINT"
           Described in perlguts.

              SAVEINT(int i)

       "save_item"
           Described in perlguts.

            void  save_item(SV* item)

       "SAVEIV"
           Described in perlguts.

              SAVEIV(IV i)

       "save_list"
           "DEPRECATED!"  It is planned to remove "save_list" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Described in perlguts.

            void  save_list(SV** sarg, I32 maxsarg)

       "SAVELONG"
           Described in perlguts.

              SAVELONG(long i)

       "SAVEMORTALIZESV"
           Described in perlguts.

              SAVEMORTALIZESV(SV* sv)

       "SAVEPPTR"
           Described in perlguts.

              SAVEPPTR(char * p)

       "save_scalar"
           Described in perlguts.

            SV*  save_scalar(GV* gv)

       "SAVESPTR"
           Described in perlguts.

              SAVESPTR(SV * s)

       "SAVESTACK_POS"
           Described in perlguts.

              SAVESTACK_POS()

       "save_svref"
           Described in perlguts.

            SV*  save_svref(SV** sptr)

       "SP"
           Stack pointer.  This is usually handled by "xsubpp".  See "dSP" and
           "SPAGAIN".

       "SPAGAIN"
           Refetch the stack pointer.  Used after a callback.  See perlcall.

              SPAGAIN;

       "TARG"
           "TARG" is short for "target".  It is an entry in the pad that an
           OPs "op_targ" refers to.  It is scratchpad space, often used as a
           return value for the OP, but some use it for other purposes.

              TARG;

       "UNOP"
           Described in perlguts.

       "XPUSHi"
           Push an integer onto the stack, extending the stack if necessary.
           Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should
           be called to declare it.  Do not call multiple "TARG"-oriented
           macros to return lists from XSUB's - see "mXPUSHi" instead.  See
           also "PUSHi" and "mPUSHi".

            void  XPUSHi(IV iv)

       "XPUSHmortal"
           Push a new mortal SV onto the stack, extending the stack if
           necessary.  Does not use "TARG".  See also "XPUSHs", "PUSHmortal"
           and "PUSHs".

            void  XPUSHmortal

       "XPUSHn"
           Push a double onto the stack, extending the stack if necessary.
           Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should
           be called to declare it.  Do not call multiple "TARG"-oriented
           macros to return lists from XSUB's - see "mXPUSHn" instead.  See
           also "PUSHn" and "mPUSHn".

            void  XPUSHn(NV nv)

       "XPUSHp"
           Push a string onto the stack, extending the stack if necessary.
           The "len" indicates the length of the string.  Handles 'set' magic.
           Uses "TARG", so "dTARGET" or "dXSTARG" should be called to declare
           it.  Do not call multiple "TARG"-oriented macros to return lists
           from XSUB's - see "mXPUSHp" instead.  See also "PUSHp" and
           "mPUSHp".

            void  XPUSHp(char* str, STRLEN len)

       "XPUSHs"
           Push an SV onto the stack, extending the stack if necessary.  Does
           not handle 'set' magic.  Does not use "TARG".  See also
           "XPUSHmortal", "PUSHs" and "PUSHmortal".

            void  XPUSHs(SV* sv)

       "XPUSHu"
           Push an unsigned integer onto the stack, extending the stack if
           necessary.  Handles 'set' magic.  Uses "TARG", so "dTARGET" or
           "dXSTARG" should be called to declare it.  Do not call multiple
           "TARG"-oriented macros to return lists from XSUB's - see "mXPUSHu"
           instead.  See also "PUSHu" and "mPUSHu".

            void  XPUSHu(UV uv)

       "XS_APIVERSION_BOOTCHECK"
           Macro to verify that the perl api version an XS module has been
           compiled against matches the api version of the perl interpreter
           it's being loaded into.

              XS_APIVERSION_BOOTCHECK;

       "XSRETURN"
           Return from XSUB, indicating number of items on the stack.  This is
           usually handled by "xsubpp".

            void  XSRETURN(int nitems)

       "XSRETURN_EMPTY"
           Return an empty list from an XSUB immediately.

              XSRETURN_EMPTY;

       "XSRETURN_IV"
           Return an integer from an XSUB immediately.  Uses "XST_mIV".

            void  XSRETURN_IV(IV iv)

       "XSRETURN_NO"
           Return &PL_sv_no from an XSUB immediately.  Uses "XST_mNO".

              XSRETURN_NO;

       "XSRETURN_NV"
           Return a double from an XSUB immediately.  Uses "XST_mNV".

            void  XSRETURN_NV(NV nv)

       "XSRETURN_PV"
           Return a copy of a string from an XSUB immediately.  Uses
           "XST_mPV".

            void  XSRETURN_PV(char* str)

       "XSRETURN_UNDEF"
           Return &PL_sv_undef from an XSUB immediately.  Uses "XST_mUNDEF".

              XSRETURN_UNDEF;

       "XSRETURN_UV"
           Return an integer from an XSUB immediately.  Uses "XST_mUV".

            void  XSRETURN_UV(IV uv)

       "XSRETURN_YES"
           Return &PL_sv_yes from an XSUB immediately.  Uses "XST_mYES".

              XSRETURN_YES;

       "XST_mIV"
           Place an integer into the specified position "pos" on the stack.
           The value is stored in a new mortal SV.

            void  XST_mIV(int pos, IV iv)

       "XST_mNO"
           Place &PL_sv_no into the specified position "pos" on the stack.

            void  XST_mNO(int pos)

       "XST_mNV"
           Place a double into the specified position "pos" on the stack.  The
           value is stored in a new mortal SV.

            void  XST_mNV(int pos, NV nv)

       "XST_mPV"
           Place a copy of a string into the specified position "pos" on the
           stack.  The value is stored in a new mortal SV.

            void  XST_mPV(int pos, char* str)

       "XST_mUNDEF"
           Place &PL_sv_undef into the specified position "pos" on the stack.

            void  XST_mUNDEF(int pos)

       "XST_mUV"
           Place an unsigned integer into the specified position "pos" on the
           stack.  The value is stored in a new mortal SV.

            void  XST_mUV(int pos, UV uv)

       "XST_mYES"
           Place &PL_sv_yes into the specified position "pos" on the stack.

            void  XST_mYES(int pos)

       "XS_VERSION"
           The version identifier for an XS module.  This is usually handled
           automatically by "ExtUtils::MakeMaker".  See
           "XS_VERSION_BOOTCHECK".

       "XS_VERSION_BOOTCHECK"
           Macro to verify that a PM module's $VERSION variable matches the XS
           module's "XS_VERSION" variable.  This is usually handled
           automatically by "xsubpp".  See "The VERSIONCHECK: Keyword" in
           perlxs.

              XS_VERSION_BOOTCHECK;


String Handling

       See also "Unicode Support".

       "CAT2"
           This macro concatenates 2 tokens together.

            token  CAT2(token x, token y)

       "Copy"
           The XSUB-writer's interface to the C "memcpy" function.  The "src"
           is the source, "dest" is the destination, "nitems" is the number of
           items, and "type" is the type.  May fail on overlapping copies.
           See also "Move".

            void  Copy(void* src, void* dest, int nitems, type)

       "CopyD"
           Like "Copy" but returns "dest".  Useful for encouraging compilers
           to tail-call optimise.

            void *  CopyD(void* src, void* dest, int nitems, type)

       "delimcpy"
           Copy a source buffer to a destination buffer, stopping at (but not
           including) the first occurrence in the source of an unescaped
           (defined below) delimiter byte, "delim".  The source is the bytes
           between "from" and "from_end" - 1.  Similarly, the dest is "to" up
           to "to_end".

           The number of bytes copied is written to *retlen.

           Returns the position of the first uncopied "delim" in the "from"
           buffer, but if there is no such occurrence before "from_end", then
           "from_end" is returned, and the entire buffer
           "from" .. "from_end" - 1 is copied.

           If there is room in the destination available after the copy, an
           extra terminating safety "NUL" byte is appended (not included in
           the returned length).

           The error case is if the destination buffer is not large enough to
           accommodate everything that should be copied.  In this situation, a
           value larger than "to_end" - "to" is written to *retlen, and as
           much of the source as fits will be written to the destination.  Not
           having room for the safety "NUL" is not considered an error.

           In the following examples, let "x" be the delimiter, and 0
           represent a "NUL" byte (NOT the digit 0).  Then we would have

             Source     Destination
            abcxdef        abc0

           provided the destination buffer is at least 4 bytes long.

           An escaped delimiter is one which is immediately preceded by a
           single backslash.  Escaped delimiters are copied, and the copy
           continues past the delimiter; the backslash is not copied:

             Source       Destination
            abc\xdef       abcxdef0

           (provided the destination buffer is at least 8 bytes long).

           It's actually somewhat more complicated than that. A sequence of
           any odd number of backslashes escapes the following delimiter, and
           the copy continues with exactly one of the backslashes stripped.

                Source         Destination
                abc\xdef          abcxdef0
              abc\\\xdef        abc\\xdef0
            abc\\\\\xdef      abc\\\\xdef0

           (as always, if the destination is large enough)

           An even number of preceding backslashes does not escape the
           delimiter, so that the copy stops just before it, and includes all
           the backslashes (no stripping; zero is considered even):

                 Source         Destination
                 abcxdef          abc0
               abc\\xdef          abc\\0
             abc\\\\xdef          abc\\\\0

            char*  delimcpy(char* to, const char* to_end, const char* from,
                            const char* from_end, const int delim,
                            I32* retlen)

       "fbm_compile"
           Analyzes the string in order to make fast searches on it using
           "fbm_instr()" -- the Boyer-Moore algorithm.

            void  fbm_compile(SV* sv, U32 flags)

       "fbm_instr"
           Returns the location of the SV in the string delimited by "big" and
           "bigend" ("bigend") is the char following the last char).  It
           returns "NULL" if the string can't be found.  The "sv" does not
           have to be "fbm_compiled", but the search will not be as fast then.

            char*  fbm_instr(unsigned char* big, unsigned char* bigend,
                             SV* littlestr, U32 flags)

       "foldEQ"
           Returns true if the leading "len" bytes of the strings "s1" and
           "s2" are the same case-insensitively; false otherwise.  Uppercase
           and lowercase ASCII range bytes match themselves and their opposite
           case counterparts.  Non-cased and non-ASCII range bytes match only
           themselves.

            I32  foldEQ(const char* a, const char* b, I32 len)

       "ibcmp"
           This is a synonym for "(! foldEQ())"

            I32  ibcmp(const char* a, const char* b, I32 len)

       "ibcmp_locale"
           This is a synonym for "(! foldEQ_locale())"

            I32  ibcmp_locale(const char* a, const char* b, I32 len)

       "ibcmp_utf8"
           This is a synonym for "(! foldEQ_utf8())"

            I32  ibcmp_utf8(const char *s1, char **pe1, UV l1, bool u1,
                            const char *s2, char **pe2, UV l2, bool u2)

       "instr"
           Same as strstr(3), which finds and returns a pointer to the first
           occurrence of the NUL-terminated substring "little" in the NUL-
           terminated string "big", returning NULL if not found.  The
           terminating NUL bytes are not compared.

            char*  instr(const char* big, const char* little)

       "memCHRs"
           Returns the position of the first occurence of the byte "c" in the
           literal string "list", or NULL if "c" doesn't appear in "list".
           All bytes are treated as unsigned char.  Thus this macro can be
           used to determine if "c" is in a set of particular characters.
           Unlike strchr(3), it works even if "c" is "NUL" (and the set
           doesn't include "NUL").

            bool  memCHRs("list", char c)

       "memEQ"
           Test two buffers (which may contain embedded "NUL" characters, to
           see if they are equal.  The "len" parameter indicates the number of
           bytes to compare.  Returns true or false.  It is undefined behavior
           if either of the buffers doesn't contain at least "len" bytes.

            bool  memEQ(char* s1, char* s2, STRLEN len)

       "memEQs"
           Like "memEQ", but the second string is a literal enclosed in double
           quotes, "l1" gives the number of bytes in "s1".  Returns true or
           false.

            bool  memEQs(char* s1, STRLEN l1, "s2")

       "memNE"
           Test two buffers (which may contain embedded "NUL" characters, to
           see if they are not equal.  The "len" parameter indicates the
           number of bytes to compare.  Returns true or false.  It is
           undefined behavior if either of the buffers doesn't contain at
           least "len" bytes.

            bool  memNE(char* s1, char* s2, STRLEN len)

       "memNEs"
           Like "memNE", but the second string is a literal enclosed in double
           quotes, "l1" gives the number of bytes in "s1".  Returns true or
           false.

            bool  memNEs(char* s1, STRLEN l1, "s2")

       "Move"
           The XSUB-writer's interface to the C "memmove" function.  The "src"
           is the source, "dest" is the destination, "nitems" is the number of
           items, and "type" is the type.  Can do overlapping moves.  See also
           "Copy".

            void  Move(void* src, void* dest, int nitems, type)

       "MoveD"
           Like "Move" but returns "dest".  Useful for encouraging compilers
           to tail-call optimise.

            void *  MoveD(void* src, void* dest, int nitems, type)

       "my_snprintf"
           The C library "snprintf" functionality, if available and standards-
           compliant (uses "vsnprintf", actually).  However, if the
           "vsnprintf" is not available, will unfortunately use the unsafe
           "vsprintf" which can overrun the buffer (there is an overrun check,
           but that may be too late).  Consider using "sv_vcatpvf" instead, or
           getting "vsnprintf".

            int  my_snprintf(char *buffer, const Size_t len,
                             const char *format, ...)

       "my_sprintf"
           "DEPRECATED!"  It is planned to remove "my_sprintf" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Do NOT use this due to the possibility of overflowing "buffer".
           Instead use my_snprintf()

            int  my_sprintf(NN char *buffer, NN const char *pat, ...)

       "my_strlcat"
           The C library "strlcat" if available, or a Perl implementation of
           it.  This operates on C "NUL"-terminated strings.

           "my_strlcat()" appends string "src" to the end of "dst".  It will
           append at most "size - strlen(dst) - 1" characters.  It will then
           "NUL"-terminate, unless "size" is 0 or the original "dst" string
           was longer than "size" (in practice this should not happen as it
           means that either "size" is incorrect or that "dst" is not a proper
           "NUL"-terminated string).

           Note that "size" is the full size of the destination buffer and the
           result is guaranteed to be "NUL"-terminated if there is room.  Note
           that room for the "NUL" should be included in "size".

           The return value is the total length that "dst" would have if
           "size" is sufficiently large.  Thus it is the initial length of
           "dst" plus the length of "src".  If "size" is smaller than the
           return, the excess was not appended.

            Size_t  my_strlcat(char *dst, const char *src, Size_t size)

       "my_strlcpy"
           The C library "strlcpy" if available, or a Perl implementation of
           it.  This operates on C "NUL"-terminated strings.

           "my_strlcpy()" copies up to "size - 1" characters from the string
           "src" to "dst", "NUL"-terminating the result if "size" is not 0.

           The return value is the total length "src" would be if the copy
           completely succeeded.  If it is larger than "size", the excess was
           not copied.

            Size_t  my_strlcpy(char *dst, const char *src, Size_t size)

       "my_strnlen"
           The C library "strnlen" if available, or a Perl implementation of
           it.

           "my_strnlen()" computes the length of the string, up to "maxlen"
           characters.  It will never attempt to address more than "maxlen"
           characters, making it suitable for use with strings that are not
           guaranteed to be NUL-terminated.

            Size_t  my_strnlen(const char *str, Size_t maxlen)

       "my_vsnprintf"
           The C library "vsnprintf" if available and standards-compliant.
           However, if the "vsnprintf" is not available, will unfortunately
           use the unsafe "vsprintf" which can overrun the buffer (there is an
           overrun check, but that may be too late).  Consider using
           "sv_vcatpvf" instead, or getting "vsnprintf".

            int  my_vsnprintf(char *buffer, const Size_t len,
                              const char *format, va_list ap)

       "ninstr"
           Find the first (leftmost) occurrence of a sequence of bytes within
           another sequence.  This is the Perl version of "strstr()", extended
           to handle arbitrary sequences, potentially containing embedded
           "NUL" characters ("NUL" is what the initial "n" in the function
           name stands for; some systems have an equivalent, "memmem()", but
           with a somewhat different API).

           Another way of thinking about this function is finding a needle in
           a haystack.  "big" points to the first byte in the haystack.
           "big_end" points to one byte beyond the final byte in the haystack.
           "little" points to the first byte in the needle.  "little_end"
           points to one byte beyond the final byte in the needle.  All the
           parameters must be non-"NULL".

           The function returns "NULL" if there is no occurrence of "little"
           within "big".  If "little" is the empty string, "big" is returned.

           Because this function operates at the byte level, and because of
           the inherent characteristics of UTF-8 (or UTF-EBCDIC), it will work
           properly if both the needle and the haystack are strings with the
           same UTF-8ness, but not if the UTF-8ness differs.

            char*  ninstr(const char* big, const char* bigend,
                          const char* little, const char* lend)

       "Nullch"
           Null character pointer.  (No longer available when "PERL_CORE" is
           defined.)

       "rninstr"
           Like "ninstr", but instead finds the final (rightmost) occurrence
           of a sequence of bytes within another sequence, returning "NULL" if
           there is no such occurrence.

            char*  rninstr(const char* big, const char* bigend,
                           const char* little, const char* lend)

       "savepv"
           Perl's version of "strdup()".  Returns a pointer to a newly
           allocated string which is a duplicate of "pv".  The size of the
           string is determined by "strlen()", which means it may not contain
           embedded "NUL" characters and must have a trailing "NUL".  To
           prevent memory leaks, the memory allocated for the new string needs
           to be freed when no longer needed.  This can be done with the
           "Safefree" function, or "SAVEFREEPV".

           On some platforms, Windows for example, all allocated memory owned
           by a thread is deallocated when that thread ends.  So if you need
           that not to happen, you need to use the shared memory functions,
           such as "savesharedpv".

            char*  savepv(const char* pv)

       "savepvn"
           Perl's version of what "strndup()" would be if it existed.  Returns
           a pointer to a newly allocated string which is a duplicate of the
           first "len" bytes from "pv", plus a trailing "NUL" byte.  The
           memory allocated for the new string can be freed with the
           "Safefree()" function.

           On some platforms, Windows for example, all allocated memory owned
           by a thread is deallocated when that thread ends.  So if you need
           that not to happen, you need to use the shared memory functions,
           such as "savesharedpvn".

            char*  savepvn(const char* pv, Size_t len)

       "savepvs"
           Like "savepvn", but takes a literal string instead of a
           string/length pair.

            char*  savepvs("literal string")

       "savesharedpv"
           A version of "savepv()" which allocates the duplicate string in
           memory which is shared between threads.

            char*  savesharedpv(const char* pv)

       "savesharedpvn"
           A version of "savepvn()" which allocates the duplicate string in
           memory which is shared between threads.  (With the specific
           difference that a "NULL" pointer is not acceptable)

            char*  savesharedpvn(const char *const pv, const STRLEN len)

       "savesharedpvs"
           A version of "savepvs()" which allocates the duplicate string in
           memory which is shared between threads.

            char*  savesharedpvs("literal string")

       "savesharedsvpv"
           A version of "savesharedpv()" which allocates the duplicate string
           in memory which is shared between threads.

            char*  savesharedsvpv(SV *sv)

       "savesvpv"
           A version of "savepv()"/"savepvn()" which gets the string to
           duplicate from the passed in SV using "SvPV()"

           On some platforms, Windows for example, all allocated memory owned
           by a thread is deallocated when that thread ends.  So if you need
           that not to happen, you need to use the shared memory functions,
           such as "savesharedsvpv".

            char*  savesvpv(SV* sv)

       "strEQ"
           Test two "NUL"-terminated strings to see if they are equal.
           Returns true or false.

            bool  strEQ(char* s1, char* s2)

       "strGE"
           Test two "NUL"-terminated strings to see if the first, "s1", is
           greater than or equal to the second, "s2".  Returns true or false.

            bool  strGE(char* s1, char* s2)

       "strGT"
           Test two "NUL"-terminated strings to see if the first, "s1", is
           greater than the second, "s2".  Returns true or false.

            bool  strGT(char* s1, char* s2)

       "STRINGIFY"
           This macro surrounds its token with double quotes.

            string  STRINGIFY(token x)

       "strLE"
           Test two "NUL"-terminated strings to see if the first, "s1", is
           less than or equal to the second, "s2".  Returns true or false.

            bool  strLE(char* s1, char* s2)

       "strLT"
           Test two "NUL"-terminated strings to see if the first, "s1", is
           less than the second, "s2".  Returns true or false.

            bool  strLT(char* s1, char* s2)

       "strNE"
           Test two "NUL"-terminated strings to see if they are different.
           Returns true or false.

            bool  strNE(char* s1, char* s2)

       "strnEQ"
           Test two "NUL"-terminated strings to see if they are equal.  The
           "len" parameter indicates the number of bytes to compare.  Returns
           true or false.  (A wrapper for "strncmp").

            bool  strnEQ(char* s1, char* s2, STRLEN len)

       "strnNE"
           Test two "NUL"-terminated strings to see if they are different.
           The "len" parameter indicates the number of bytes to compare.
           Returns true or false.  (A wrapper for "strncmp").

            bool  strnNE(char* s1, char* s2, STRLEN len)

       "STR_WITH_LEN"
           Returns two comma separated tokens of the input literal string, and
           its length.  This is convenience macro which helps out in some API
           calls.  Note that it can't be used as an argument to macros or
           functions that under some configurations might be macros, which
           means that it requires the full Perl_xxx(aTHX_ ...) form for any
           API calls where it's used.

            pair  STR_WITH_LEN("literal string")

       "Zero"
           The XSUB-writer's interface to the C "memzero" function.  The
           "dest" is the destination, "nitems" is the number of items, and
           "type" is the type.

            void  Zero(void* dest, int nitems, type)

       "ZeroD"
           Like "Zero" but returns dest.  Useful for encouraging compilers to
           tail-call optimise.

            void *  ZeroD(void* dest, int nitems, type)


SV Flags

       "SVt_IV"
           Type flag for scalars.  See "svtype".

       "SVt_NULL"
           Type flag for scalars.  See "svtype".

       "SVt_NV"
           Type flag for scalars.  See "svtype".

       "SVt_PV"
           Type flag for scalars.  See "svtype".

       "SVt_PVAV"
           Type flag for arrays.  See "svtype".

       "SVt_PVCV"
           Type flag for subroutines.  See "svtype".

       "SVt_PVFM"
           Type flag for formats.  See "svtype".

       "SVt_PVGV"
           Type flag for typeglobs.  See "svtype".

       "SVt_PVHV"
           Type flag for hashes.  See "svtype".

       "SVt_PVIO"
           Type flag for I/O objects.  See "svtype".

       "SVt_PVIV"
           Type flag for scalars.  See "svtype".

       "SVt_PVLV"
           Type flag for scalars.  See "svtype".

       "SVt_PVMG"
           Type flag for scalars.  See "svtype".

       "SVt_PVNV"
           Type flag for scalars.  See "svtype".

       "SVt_REGEXP"
           Type flag for regular expressions.  See "svtype".

       "svtype"
           An enum of flags for Perl types.  These are found in the file sv.h
           in the "svtype" enum.  Test these flags with the "SvTYPE" macro.

           The types are:

               SVt_NULL
               SVt_IV
               SVt_NV
               SVt_RV
               SVt_PV
               SVt_PVIV
               SVt_PVNV
               SVt_PVMG
               SVt_INVLIST
               SVt_REGEXP
               SVt_PVGV
               SVt_PVLV
               SVt_PVAV
               SVt_PVHV
               SVt_PVCV
               SVt_PVFM
               SVt_PVIO

           These are most easily explained from the bottom up.

           "SVt_PVIO" is for I/O objects, "SVt_PVFM" for formats, "SVt_PVCV"
           for subroutines, "SVt_PVHV" for hashes and "SVt_PVAV" for arrays.

           All the others are scalar types, that is, things that can be bound
           to a "$" variable.  For these, the internal types are mostly
           orthogonal to types in the Perl language.

           Hence, checking "SvTYPE(sv) < SVt_PVAV" is the best way to see
           whether something is a scalar.

           "SVt_PVGV" represents a typeglob.  If "!SvFAKE(sv)", then it is a
           real, incoercible typeglob.  If "SvFAKE(sv)", then it is a scalar
           to which a typeglob has been assigned.  Assigning to it again will
           stop it from being a typeglob.  "SVt_PVLV" represents a scalar that
           delegates to another scalar behind the scenes.  It is used, e.g.,
           for the return value of "substr" and for tied hash and array
           elements.  It can hold any scalar value, including a typeglob.
           "SVt_REGEXP" is for regular expressions.  "SVt_INVLIST" is for Perl
           core internal use only.

           "SVt_PVMG" represents a "normal" scalar (not a typeglob, regular
           expression, or delegate).  Since most scalars do not need all the
           internal fields of a PVMG, we save memory by allocating smaller
           structs when possible.  All the other types are just simpler forms
           of "SVt_PVMG", with fewer internal fields.  "SVt_NULL" can only
           hold undef.  "SVt_IV" can hold undef, an integer, or a reference.
           ("SVt_RV" is an alias for "SVt_IV", which exists for backward
           compatibility.)  "SVt_NV" can hold any of those or a double.
           "SVt_PV" can only hold "undef" or a string.  "SVt_PVIV" is a
           superset of "SVt_PV" and "SVt_IV".  "SVt_PVNV" is similar.
           "SVt_PVMG" can hold anything "SVt_PVNV" can hold, but it can, but
           does not have to, be blessed or magical.


SV Handling

       An SV (or AV, HV, etc.) is allocated in two parts: the head (struct sv,
       av, hv...) contains type and reference count information, and for many
       types, a pointer to the body (struct xrv, xpv, xpviv...), which
       contains fields specific to each type.  Some types store all they need
       in the head, so don't have a body.

       In all but the most memory-paranoid configurations (ex: PURIFY), heads
       and bodies are allocated out of arenas, which by default are
       approximately 4K chunks of memory parcelled up into N heads or bodies.
       Sv-bodies are allocated by their sv-type, guaranteeing size consistency
       needed to allocate safely from arrays.

       For SV-heads, the first slot in each arena is reserved, and holds a
       link to the next arena, some flags, and a note of the number of slots.
       Snaked through each arena chain is a linked list of free items; when
       this becomes empty, an extra arena is allocated and divided up into N
       items which are threaded into the free list.

       SV-bodies are similar, but they use arena-sets by default, which
       separate the link and info from the arena itself, and reclaim the 1st
       slot in the arena.  SV-bodies are further described later.

       The following global variables are associated with arenas:

        PL_sv_arenaroot     pointer to list of SV arenas
        PL_sv_root          pointer to list of free SV structures

        PL_body_arenas      head of linked-list of body arenas
        PL_body_roots[]     array of pointers to list of free bodies of svtype
                            arrays are indexed by the svtype needed

       A few special SV heads are not allocated from an arena, but are instead
       directly created in the interpreter structure, eg PL_sv_undef.  The
       size of arenas can be changed from the default by setting
       PERL_ARENA_SIZE appropriately at compile time.

       The SV arena serves the secondary purpose of allowing still-live SVs to
       be located and destroyed during final cleanup.

       At the lowest level, the macros new_SV() and del_SV() grab and free an
       SV head.  (If debugging with -DD, del_SV() calls the function
       S_del_sv() to return the SV to the free list with error checking.)
       new_SV() calls more_sv() / sv_add_arena() to add an extra arena if the
       free list is empty.  SVs in the free list have their SvTYPE field set
       to all ones.

       At the time of very final cleanup, sv_free_arenas() is called from
       perl_destruct() to physically free all the arenas allocated since the
       start of the interpreter.

       The internal function visit() scans the SV arenas list, and calls a
       specified function for each SV it finds which is still live, i.e. which
       has an SvTYPE other than all 1's, and a non-zero SvREFCNT. visit() is
       used by the following functions (specified as [function that calls
       visit()] / [function called by visit() for each SV]):

           sv_report_used() / do_report_used()
                               dump all remaining SVs (debugging aid)

           sv_clean_objs() / do_clean_objs(),do_clean_named_objs(),
                             do_clean_named_io_objs(),do_curse()
                               Attempt to free all objects pointed to by RVs,
                               try to do the same for all objects indir-
                               ectly referenced by typeglobs too, and
                               then do a final sweep, cursing any
                               objects that remain.  Called once from
                               perl_destruct(), prior to calling sv_clean_all()
                               below.

           sv_clean_all() / do_clean_all()
                               SvREFCNT_dec(sv) each remaining SV, possibly
                               triggering an sv_free(). It also sets the
                               SVf_BREAK flag on the SV to indicate that the
                               refcnt has been artificially lowered, and thus
                               stopping sv_free() from giving spurious warnings
                               about SVs which unexpectedly have a refcnt
                               of zero.  called repeatedly from perl_destruct()
                               until there are no SVs left.

   Arena allocator API Summary
       Private API to rest of sv.c

           new_SV(),  del_SV(),

           new_XPVNV(), del_XPVGV(),
           etc

       Public API:

           sv_report_used(), sv_clean_objs(), sv_clean_all(), sv_free_arenas()

       "boolSV"
           Returns a true SV if "b" is a true value, or a false SV if "b" is
           0.

           See also "PL_sv_yes" and "PL_sv_no".

            SV *  boolSV(bool b)

       "croak_xs_usage"
           A specialised variant of "croak()" for emitting the usage message
           for xsubs

               croak_xs_usage(cv, "eee_yow");

           works out the package name and subroutine name from "cv", and then
           calls "croak()".  Hence if "cv" is &ouch::awk, it would call
           "croak" as:

            Perl_croak(aTHX_ "Usage: %" SVf "::%" SVf "(%s)", "ouch" "awk",
                                                                "eee_yow");

            void  croak_xs_usage(const CV *const cv, const char *const params)

       "DEFSV"
           Returns the SV associated with $_

            SV *  DEFSV

       "DEFSV_set"
           Associate "sv" with $_

            void  DEFSV_set(SV * sv)

       "get_sv"
           Returns the SV of the specified Perl scalar.  "flags" are passed to
           "gv_fetchpv".  If "GV_ADD" is set and the Perl variable does not
           exist then it will be created.  If "flags" is zero and the variable
           does not exist then NULL is returned.

           NOTE: the "perl_get_sv()" form is deprecated.

            SV*  get_sv(const char *name, I32 flags)

       "isGV_with_GP"
           Returns a boolean as to whether or not "sv" is a GV with a pointer
           to a GP (glob pointer).

            bool  isGV_with_GP(SV * sv)

       "looks_like_number"
           Test if the content of an SV looks like a number (or is a number).
           "Inf" and "Infinity" are treated as numbers (so will not issue a
           non-numeric warning), even if your "atof()" doesn't grok them.
           Get-magic is ignored.

            I32  looks_like_number(SV *const sv)

       "MUTABLE_PTR"
       "MUTABLE_AV"
       "MUTABLE_CV"
       "MUTABLE_GV"
       "MUTABLE_HV"
       "MUTABLE_IO"
       "MUTABLE_SV"
           The "MUTABLE_*"() macros cast pointers to the types shown, in such
           a way (compiler permitting) that casting away const-ness will give
           a warning; e.g.:

            const SV *sv = ...;
            AV *av1 = (AV*)sv;        <== BAD:  the const has been silently
                                                cast away
            AV *av2 = MUTABLE_AV(sv); <== GOOD: it may warn

           "MUTABLE_PTR" is the base macro used to derive new casts.  The
           other already-built-in ones return pointers to what their names
           indicate.

            void *  MUTABLE_PTR(void * p)
            AV *    MUTABLE_AV (AV * p)
            CV *    MUTABLE_CV (CV * p)
            GV *    MUTABLE_GV (GV * p)
            HV *    MUTABLE_HV (HV * p)
            IO *    MUTABLE_IO (IO * p)
            SV *    MUTABLE_SV (SV * p)

       "newRV"
       "newRV_inc"
           These are identical.  They create an RV wrapper for an SV.  The
           reference count for the original SV is incremented.

            SV*  newRV(SV *const sv)

       "newRV_noinc"
           Creates an RV wrapper for an SV.  The reference count for the
           original SV is not incremented.

            SV*  newRV_noinc(SV *const tmpRef)

       "newSV"
           Creates a new SV.  A non-zero "len" parameter indicates the number
           of bytes of preallocated string space the SV should have.  An extra
           byte for a trailing "NUL" is also reserved.  ("SvPOK" is not set
           for the SV even if string space is allocated.)  The reference count
           for the new SV is set to 1.

           In 5.9.3, "newSV()" replaces the older "NEWSV()" API, and drops the
           first parameter, x, a debug aid which allowed callers to identify
           themselves.  This aid has been superseded by a new build option,
           "PERL_MEM_LOG" (see "PERL_MEM_LOG" in perlhacktips).  The older API
           is still there for use in XS modules supporting older perls.

            SV*  newSV(const STRLEN len)

       "newSVhek"
           Creates a new SV from the hash key structure.  It will generate
           scalars that point to the shared string table where possible.
           Returns a new (undefined) SV if "hek" is NULL.

            SV*  newSVhek(const HEK *const hek)

       "newSViv"
           Creates a new SV and copies an integer into it.  The reference
           count for the SV is set to 1.

            SV*  newSViv(const IV i)

       "newSVnv"
           Creates a new SV and copies a floating point value into it.  The
           reference count for the SV is set to 1.

            SV*  newSVnv(const NV n)

       "newSVpadname"
           NOTE: "newSVpadname" is experimental and may change or be removed
           without notice.

           Creates a new SV containing the pad name.

            SV*  newSVpadname(PADNAME *pn)

       "newSVpv"
           Creates a new SV and copies a string (which may contain "NUL"
           ("\0") characters) into it.  The reference count for the SV is set
           to 1.  If "len" is zero, Perl will compute the length using
           "strlen()", (which means if you use this option, that "s" can't
           have embedded "NUL" characters and has to have a terminating "NUL"
           byte).

           This function can cause reliability issues if you are likely to
           pass in empty strings that are not null terminated, because it will
           run strlen on the string and potentially run past valid memory.

           Using "newSVpvn" is a safer alternative for non "NUL" terminated
           strings.  For string literals use "newSVpvs" instead.  This
           function will work fine for "NUL" terminated strings, but if you
           want to avoid the if statement on whether to call "strlen" use
           "newSVpvn" instead (calling "strlen" yourself).

            SV*  newSVpv(const char *const s, const STRLEN len)

       "newSVpvf"
           Creates a new SV and initializes it with the string formatted like
           "sv_catpvf".

           NOTE: "newSVpvf" must be explicitly called as "Perl_newSVpvf" with
           an "aTHX_" parameter.

            SV*  Perl_newSVpvf(pTHX_ const char *const pat, ...)

       "newSVpvf_nocontext"
           Like "newSVpvf" but does not take a thread context ("aTHX")
           parameter, so is used in situations where the caller doesn't
           already have the thread context.

            SV*  newSVpvf_nocontext(const char *const pat, ...)

       "newSVpvn"
           Creates a new SV and copies a string into it, which may contain
           "NUL" characters ("\0") and other binary data.  The reference count
           for the SV is set to 1.  Note that if "len" is zero, Perl will
           create a zero length (Perl) string.  You are responsible for
           ensuring that the source buffer is at least "len" bytes long.  If
           the "buffer" argument is NULL the new SV will be undefined.

            SV*  newSVpvn(const char *const buffer, const STRLEN len)

       "newSVpvn_flags"
           Creates a new SV and copies a string (which may contain "NUL"
           ("\0") characters) into it.  The reference count for the SV is set
           to 1.  Note that if "len" is zero, Perl will create a zero length
           string.  You are responsible for ensuring that the source string is
           at least "len" bytes long.  If the "s" argument is NULL the new SV
           will be undefined.  Currently the only flag bits accepted are
           "SVf_UTF8" and "SVs_TEMP".  If "SVs_TEMP" is set, then
           "sv_2mortal()" is called on the result before returning.  If
           "SVf_UTF8" is set, "s" is considered to be in UTF-8 and the
           "SVf_UTF8" flag will be set on the new SV.  "newSVpvn_utf8()" is a
           convenience wrapper for this function, defined as

               #define newSVpvn_utf8(s, len, u)                    \
                   newSVpvn_flags((s), (len), (u) ? SVf_UTF8 : 0)

            SV*  newSVpvn_flags(const char *const s, const STRLEN len,
                                const U32 flags)

       "newSVpvn_share"
           Creates a new SV with its "SvPVX_const" pointing to a shared string
           in the string table.  If the string does not already exist in the
           table, it is created first.  Turns on the "SvIsCOW" flag (or
           "READONLY" and "FAKE" in 5.16 and earlier).  If the "hash"
           parameter is non-zero, that value is used; otherwise the hash is
           computed.  The string's hash can later be retrieved from the SV
           with the "SvSHARED_HASH" macro.  The idea here is that as the
           string table is used for shared hash keys these strings will have
           "SvPVX_const == HeKEY" and hash lookup will avoid string compare.

            SV*  newSVpvn_share(const char* s, I32 len, U32 hash)

       "newSVpvn_utf8"
           Creates a new SV and copies a string (which may contain "NUL"
           ("\0") characters) into it.  If "utf8" is true, calls "SvUTF8_on"
           on the new SV.  Implemented as a wrapper around "newSVpvn_flags".

            SV*  newSVpvn_utf8(const char* s, STRLEN len, U32 utf8)

       "newSVpvs"
           Like "newSVpvn", but takes a literal string instead of a
           string/length pair.

            SV*  newSVpvs("literal string")

       "newSVpvs_flags"
           Like "newSVpvn_flags", but takes a literal string instead of a
           string/length pair.

            SV*  newSVpvs_flags("literal string", U32 flags)

       "newSVpv_share"
           Like "newSVpvn_share", but takes a "NUL"-terminated string instead
           of a string/length pair.

            SV*  newSVpv_share(const char* s, U32 hash)

       "newSVpvs_share"
           Like "newSVpvn_share", but takes a literal string instead of a
           string/length pair and omits the hash parameter.

            SV*  newSVpvs_share("literal string")

       "newSVrv"
           Creates a new SV for the existing RV, "rv", to point to.  If "rv"
           is not an RV then it will be upgraded to one.  If "classname" is
           non-null then the new SV will be blessed in the specified package.
           The new SV is returned and its reference count is 1.  The reference
           count 1 is owned by "rv". See also newRV_inc() and newRV_noinc()
           for creating a new RV properly.

            SV*  newSVrv(SV *const rv, const char *const classname)

       "newSVsv"
       "newSVsv_nomg"
       "newSVsv_flags"
           These create a new SV which is an exact duplicate of the original
           SV (using "sv_setsv".)

           They differ only in that "newSVsv" performs 'get' magic;
           "newSVsv_nomg" skips any magic; and "newSVsv_flags" allows you to
           explicitly set a "flags" parameter.

            SV*  newSVsv      (SV *const old)
            SV*  newSVsv_nomg (SV *const old)
            SV*  newSVsv_flags(SV *const old, I32 flags)

       "newSV_type"
           Creates a new SV, of the type specified.  The reference count for
           the new SV is set to 1.

            SV*  newSV_type(const svtype type)

       "newSVuv"
           Creates a new SV and copies an unsigned integer into it.  The
           reference count for the SV is set to 1.

            SV*  newSVuv(const UV u)

       "Nullsv"
           Null SV pointer.  (No longer available when "PERL_CORE" is
           defined.)

       "PL_na"
           A convenience variable which is typically used with "SvPV" when one
           doesn't care about the length of the string.  It is usually more
           efficient to either declare a local variable and use that instead
           or to use the "SvPV_nolen" macro.

            STRLEN  PL_na

       "PL_sv_no"
           This is the "false" SV.  It is readonly.  See "PL_sv_yes".  Always
           refer to this as &PL_sv_no.

            SV  PL_sv_no

       "PL_sv_undef"
           This is the "undef" SV.  It is readonly.  Always refer to this as
           &PL_sv_undef.

            SV  PL_sv_undef

       "PL_sv_yes"
           This is the "true" SV.  It is readonly.  See "PL_sv_no".  Always
           refer to this as &PL_sv_yes.

            SV  PL_sv_yes

       "PL_sv_zero"
           This readonly SV has a zero numeric value and a "0" string value.
           It's similar to "PL_sv_no" except for its string value. Can be used
           as a cheap alternative to mXPUSHi(0) for example.  Always refer to
           this as &PL_sv_zero. Introduced in 5.28.

            SV  PL_sv_zero

       "SAVE_DEFSV"
           Localize $_.  See "Localizing changes" in perlguts.

            void  SAVE_DEFSV

       "sortsv"
           In-place sort an array of SV pointers with the given comparison
           routine.

           Currently this always uses mergesort.  See "sortsv_flags" for a
           more flexible routine.

            void  sortsv(SV** array, size_t num_elts, SVCOMPARE_t cmp)

       "sortsv_flags"
           In-place sort an array of SV pointers with the given comparison
           routine, with various SORTf_* flag options.

            void  sortsv_flags(SV** array, size_t num_elts, SVCOMPARE_t cmp,
                               U32 flags)

       "SV"
           Described in perlguts.

       "sv_2cv"
           Using various gambits, try to get a CV from an SV; in addition, try
           if possible to set *st and *gvp to the stash and GV associated with
           it.  The flags in "lref" are passed to "gv_fetchsv".

            CV*  sv_2cv(SV* sv, HV **const st, GV **const gvp, const I32 lref)

       "sv_2io"
           Using various gambits, try to get an IO from an SV: the IO slot if
           its a GV; or the recursive result if we're an RV; or the IO slot of
           the symbol named after the PV if we're a string.

           'Get' magic is ignored on the "sv" passed in, but will be called on
           "SvRV(sv)" if "sv" is an RV.

            IO*  sv_2io(SV *const sv)

       "sv_2iv_flags"
           Return the integer value of an SV, doing any necessary string
           conversion.  If "flags" has the "SV_GMAGIC" bit set, does an
           "mg_get()" first.  Normally used via the "SvIV(sv)" and "SvIVx(sv)"
           macros.

            IV  sv_2iv_flags(SV *const sv, const I32 flags)

       "sv_2mortal"
           Marks an existing SV as mortal.  The SV will be destroyed "soon",
           either by an explicit call to "FREETMPS", or by an implicit call at
           places such as statement boundaries.  "SvTEMP()" is turned on which
           means that the SV's string buffer can be "stolen" if this SV is
           copied.  See also "sv_newmortal" and "sv_mortalcopy".

            SV*  sv_2mortal(SV *const sv)

       "sv_2nv_flags"
           Return the num value of an SV, doing any necessary string or
           integer conversion.  If "flags" has the "SV_GMAGIC" bit set, does
           an "mg_get()" first.  Normally used via the "SvNV(sv)" and
           "SvNVx(sv)" macros.

            NV  sv_2nv_flags(SV *const sv, const I32 flags)

       "sv_2pvbyte"
           Returns a pointer to the byte-encoded representation of the SV, and
           set *lp to its length.  If the SV is marked as being encoded as
           UTF-8, it will downgrade it to a byte string as a side-effect, if
           possible.  If the SV cannot be downgraded, this croaks.

           Processes 'get' magic.

           Usually accessed via the "SvPVbyte" macro.

            char*  sv_2pvbyte(SV *sv, STRLEN *const lp)

       "sv_2pvutf8"
           Return a pointer to the UTF-8-encoded representation of the SV, and
           set *lp to its length.  May cause the SV to be upgraded to UTF-8 as
           a side-effect.

           Usually accessed via the "SvPVutf8" macro.

            char*  sv_2pvutf8(SV *sv, STRLEN *const lp)

       "sv_2uv_flags"
           Return the unsigned integer value of an SV, doing any necessary
           string conversion.  If "flags" has the "SV_GMAGIC" bit set, does an
           "mg_get()" first.  Normally used via the "SvUV(sv)" and "SvUVx(sv)"
           macros.

            UV  sv_2uv_flags(SV *const sv, const I32 flags)

       "sv_backoff"
           Remove any string offset.  You should normally use the "SvOOK_off"
           macro wrapper instead.

            void  sv_backoff(SV *const sv)

       "sv_bless"
           Blesses an SV into a specified package.  The SV must be an RV.  The
           package must be designated by its stash (see "gv_stashpv").  The
           reference count of the SV is unaffected.

            SV*  sv_bless(SV *const sv, HV *const stash)

       "sv_catpv"
       "sv_catpv_flags"
       "sv_catpv_mg"
       "sv_catpv_nomg"
           These concatenate the "NUL"-terminated string "sstr" onto the end
           of the string which is in the SV.  If the SV has the UTF-8 status
           set, then the bytes appended should be valid UTF-8.

           They differ only in how they handle magic:

           "sv_catpv_mg" performs both 'get' and 'set' magic.

           "sv_catpv" performs only 'get' magic.

           "sv_catpv_nomg" skips all magic.

           "sv_catpv_flags" has an extra "flags" parameter which allows you to
           specify any combination of magic handling (using "SV_GMAGIC" and/or
           "SV_SMAGIC"), and to also override the UTF-8 handling.  By
           supplying the "SV_CATUTF8" flag, the appended string is forced to
           be interpreted as UTF-8; by supplying instead the "SV_CATBYTES"
           flag, it will be interpreted as just bytes.  Either the SV or the
           string appended will be upgraded to UTF-8 if necessary.

            void  sv_catpv      (SV *const dsv, const char* sstr)
            void  sv_catpv_flags(SV *dsv, const char *sstr, const I32 flags)
            void  sv_catpv_mg   (SV *const dsv, const char *const sstr)
            void  sv_catpv_nomg (SV *const dsv, const char* sstr)

       "sv_catpvf"
       "sv_catpvf_nocontext"
       "sv_catpvf_mg"
       "sv_catpvf_mg_nocontext"
           These process their arguments like "sprintf", and append the
           formatted output to an SV.  As with "sv_vcatpvfn", argument
           reordering is not supporte when called with a non-null C-style
           variable argument list.

           If the appended data contains "wide" characters (including, but not
           limited to, SVs with a UTF-8 PV formatted with %s, and characters
           >255 formatted with %c), the original SV might get upgraded to
           UTF-8.

           If the original SV was UTF-8, the pattern should be valid UTF-8; if
           the original SV was bytes, the pattern should be too.

           All perform 'get' magic, but only "sv_catpvf_mg" and
           "sv_catpvf_mg_nocontext" perform 'set' magic.

           "sv_catpvf_nocontext" and "sv_catpvf_mg_nocontext" do not take a
           thread context ("aTHX") parameter, so are used in situations where
           the caller doesn't already have the thread context.

           NOTE: "sv_catpvf" must be explicitly called as "Perl_sv_catpvf"
           with an "aTHX_" parameter.

           NOTE: "sv_catpvf_mg" must be explicitly called as
           "Perl_sv_catpvf_mg" with an "aTHX_" parameter.

            void  Perl_sv_catpvf        (pTHX_ SV *const sv,
                                         const char *const pat, ...)
            void  sv_catpvf_nocontext   (SV *const sv, const char *const pat,
                                         ...)
            void  Perl_sv_catpvf_mg     (pTHX_ SV *const sv,
                                         const char *const pat, ...)
            void  sv_catpvf_mg_nocontext(SV *const sv, const char *const pat,
                                         ...)

       "sv_catpvn"
       "sv_catpvn_flags"
       "sv_catpvn_mg"
       "sv_catpvn_nomg"
           These concatenate the "len" bytes of the string beginning at "ptr"
           onto the end of the string which is in "dsv".  The caller must make
           sure "ptr" contains at least "len" bytes.

           For all but "sv_catpvn_flags", the string appended is assumed to be
           valid UTF-8 if the SV has the UTF-8 status set, and a string of
           bytes otherwise.

           They differ in that:

           "sv_catpvn_mg" performs both 'get' and 'set' magic on "dsv".

           "sv_catpvn" performs only 'get' magic.

           "sv_catpvn_nomg" skips all magic.

           "sv_catpvn_flags" has an extra "flags" parameter which allows you
           to specify any combination of magic handling (using "SV_GMAGIC"
           and/or "SV_SMAGIC") and to also override the UTF-8 handling.  By
           supplying the "SV_CATBYTES" flag, the appended string is
           interpreted as plain bytes; by supplying instead the "SV_CATUTF8"
           flag, it will be interpreted as UTF-8, and the "dsv" will be
           upgraded to UTF-8 if necessary.

           "sv_catpvn", "sv_catpvn_mg", and "sv_catpvn_nomg" are implemented
           in terms of "sv_catpvn_flags".

            void  sv_catpvn      (SV *dsv, const char *sstr, STRLEN len)
            void  sv_catpvn_flags(SV *const dsv, const char *sstr,
                                  const STRLEN len, const I32 flags)
            void  sv_catpvn_mg   (SV *dsv, const char *sstr, STRLEN len)
            void  sv_catpvn_nomg (SV *dsv, const char *sstr, STRLEN len)

       "sv_catpvs"
           Like "sv_catpvn", but takes a literal string instead of a
           string/length pair.

            void  sv_catpvs(SV* sv, "literal string")

       "sv_catpvs_flags"
           Like "sv_catpvn_flags", but takes a literal string instead of a
           string/length pair.

            void  sv_catpvs_flags(SV* sv, "literal string", I32 flags)

       "sv_catpvs_mg"
           Like "sv_catpvn_mg", but takes a literal string instead of a
           string/length pair.

            void  sv_catpvs_mg(SV* sv, "literal string")

       "sv_catpvs_nomg"
           Like "sv_catpvn_nomg", but takes a literal string instead of a
           string/length pair.

            void  sv_catpvs_nomg(SV* sv, "literal string")

       "sv_catsv"
       "sv_catsv_flags"
       "sv_catsv_mg"
       "sv_catsv_nomg"
           These concatenate the string from SV "sstr" onto the end of the
           string in SV "dsv".  If "sstr" is null, these are no-ops; otherwise
           only "dsv" is modified.

           They differ only in what magic they perform:

           "sv_catsv_mg" performs 'get' magic on both SVs before the copy, and
           'set' magic on "dsv" afterwards.

           "sv_catsv" performs just 'get' magic, on both SVs.

           "sv_catsv_nomg" skips all magic.

           "sv_catsv_flags" has an extra "flags" parameter which allows you to
           use "SV_GMAGIC" and/or "SV_SMAGIC" to specify any combination of
           magic handling (although either both or neither SV will have 'get'
           magic applied to it.)

           "sv_catsv", "sv_catsv_mg", and "sv_catsv_nomg" are implemented in
           terms of "sv_catsv_flags".

            void  sv_catsv      (SV *dsv, SV *sstr)
            void  sv_catsv_flags(SV *const dsv, SV *const sstr,
                                 const I32 flags)
            void  sv_catsv_mg   (SV *dsv, SV *sstr)
            void  sv_catsv_nomg (SV *dsv, SV *sstr)

       "sv_chop"
           Efficient removal of characters from the beginning of the string
           buffer.  "SvPOK(sv)", or at least "SvPOKp(sv)", must be true and
           "ptr" must be a pointer to somewhere inside the string buffer.
           "ptr" becomes the first character of the adjusted string.  Uses the
           "OOK" hack.  On return, only "SvPOK(sv)" and "SvPOKp(sv)" among the
           "OK" flags will be true.

           Beware: after this function returns, "ptr" and SvPVX_const(sv) may
           no longer refer to the same chunk of data.

           The unfortunate similarity of this function's name to that of
           Perl's "chop" operator is strictly coincidental.  This function
           works from the left; "chop" works from the right.

            void  sv_chop(SV *const sv, const char *const ptr)

       "sv_clear"
           Clear an SV: call any destructors, free up any memory used by the
           body, and free the body itself.  The SV's head is not freed,
           although its type is set to all 1's so that it won't inadvertently
           be assumed to be live during global destruction etc.  This function
           should only be called when "REFCNT" is zero.  Most of the time
           you'll want to call "sv_free()" (or its macro wrapper
           "SvREFCNT_dec") instead.

            void  sv_clear(SV *const orig_sv)

       "sv_cmp"
           Compares the strings in two SVs.  Returns -1, 0, or 1 indicating
           whether the string in "sv1" is less than, equal to, or greater than
           the string in "sv2".  Is UTF-8 and 'use bytes' aware, handles get
           magic, and will coerce its args to strings if necessary.  See also
           "sv_cmp_locale".

            I32  sv_cmp(SV *const sv1, SV *const sv2)

       "sv_cmp_flags"
           Compares the strings in two SVs.  Returns -1, 0, or 1 indicating
           whether the string in "sv1" is less than, equal to, or greater than
           the string in "sv2".  Is UTF-8 and 'use bytes' aware and will
           coerce its args to strings if necessary.  If the flags has the
           "SV_GMAGIC" bit set, it handles get magic.  See also
           "sv_cmp_locale_flags".

            I32  sv_cmp_flags(SV *const sv1, SV *const sv2, const U32 flags)

       "sv_cmp_locale"
           Compares the strings in two SVs in a locale-aware manner.  Is UTF-8
           and 'use bytes' aware, handles get magic, and will coerce its args
           to strings if necessary.  See also "sv_cmp".

            I32  sv_cmp_locale(SV *const sv1, SV *const sv2)

       "sv_cmp_locale_flags"
           Compares the strings in two SVs in a locale-aware manner.  Is UTF-8
           and 'use bytes' aware and will coerce its args to strings if
           necessary.  If the flags contain "SV_GMAGIC", it handles get magic.
           See also "sv_cmp_flags".

            I32  sv_cmp_locale_flags(SV *const sv1, SV *const sv2,
                                     const U32 flags)

       "sv_collxfrm"
           This calls "sv_collxfrm_flags" with the SV_GMAGIC flag.  See
           "sv_collxfrm_flags".

            char*  sv_collxfrm(SV *const sv, STRLEN *const nxp)

       "sv_collxfrm_flags"
           Add Collate Transform magic to an SV if it doesn't already have it.
           If the flags contain "SV_GMAGIC", it handles get-magic.

           Any scalar variable may carry "PERL_MAGIC_collxfrm" magic that
           contains the scalar data of the variable, but transformed to such a
           format that a normal memory comparison can be used to compare the
           data according to the locale settings.

            char*  sv_collxfrm_flags(SV *const sv, STRLEN *const nxp,
                                     I32 const flags)

       "sv_copypv"
       "sv_copypv_nomg"
       "sv_copypv_flags"
           These copy a stringified representation of the source SV into the
           destination SV.  They automatically perform coercion of numeric
           values into strings.  Guaranteed to preserve the "UTF8" flag even
           from overloaded objects.  Similar in nature to "sv_2pv[_flags]" but
           they operate directly on an SV instead of just the string.  Mostly
           they use ""sv_2pv_flags"" in perlintern to do the work, except when
           that would lose the UTF-8'ness of the PV.

           The three forms differ only in whether or not they perform 'get
           magic' on "sv".  "sv_copypv_nomg" skips 'get magic'; "sv_copypv"
           performs it; and "sv_copypv_flags" either performs it (if the
           "SV_GMAGIC" bit is set in "flags") or doesn't (if that bit is
           cleared).

            void  sv_copypv      (SV *const dsv, SV *const ssv)
            void  sv_copypv_nomg (SV *const dsv, SV *const ssv)
            void  sv_copypv_flags(SV *const dsv, SV *const ssv,
                                  const I32 flags)

       "SvCUR"
           Returns the length, in bytes, of the PV inside the SV.  Note that
           this may not match Perl's "length"; for that, use
           "sv_len_utf8(sv)". See "SvLEN" also.

            STRLEN  SvCUR(SV* sv)

       "SvCUR_set"
           Sets the current length, in bytes, of the C string which is in the
           SV.  See "SvCUR" and "SvIV_set">.

            void  SvCUR_set(SV* sv, STRLEN len)

       "sv_dec"
       "sv_dec_nomg"
           These auto-decrement the value in the SV, doing string to numeric
           conversion if necessary.  They both handle operator overloading.

           They differ only in that:

           "sv_dec" handles 'get' magic; "sv_dec_nomg" skips 'get' magic.

            void  sv_dec(SV *const sv)

       "sv_derived_from"
           Exactly like "sv_derived_from_pv", but doesn't take a "flags"
           parameter.

            bool  sv_derived_from(SV* sv, const char *const name)

       "sv_derived_from_pv"
           Exactly like "sv_derived_from_pvn", but takes a nul-terminated
           string instead of a string/length pair.

            bool  sv_derived_from_pv(SV* sv, const char *const name,
                                     U32 flags)

       "sv_derived_from_pvn"
           Returns a boolean indicating whether the SV is derived from the
           specified class at the C level.  To check derivation at the Perl
           level, call "isa()" as a normal Perl method.

           Currently, the only significant value for "flags" is SVf_UTF8.

            bool  sv_derived_from_pvn(SV* sv, const char *const name,
                                      const STRLEN len, U32 flags)

       "sv_derived_from_sv"
           Exactly like "sv_derived_from_pvn", but takes the name string in
           the form of an SV instead of a string/length pair. This is the
           advised form.

            bool  sv_derived_from_sv(SV* sv, SV *namesv, U32 flags)

       "sv_does"
           Like "sv_does_pv", but doesn't take a "flags" parameter.

            bool  sv_does(SV* sv, const char *const name)

       "sv_does_pv"
           Like "sv_does_sv", but takes a nul-terminated string instead of an
           SV.

            bool  sv_does_pv(SV* sv, const char *const name, U32 flags)

       "sv_does_pvn"
           Like "sv_does_sv", but takes a string/length pair instead of an SV.

            bool  sv_does_pvn(SV* sv, const char *const name,
                              const STRLEN len, U32 flags)

       "sv_does_sv"
           Returns a boolean indicating whether the SV performs a specific,
           named role.  The SV can be a Perl object or the name of a Perl
           class.

            bool  sv_does_sv(SV* sv, SV* namesv, U32 flags)

       "SvEND"
           Returns a pointer to the spot just after the last character in the
           string which is in the SV, where there is usually a trailing "NUL"
           character (even though Perl scalars do not strictly require it).
           See "SvCUR".  Access the character as "*(SvEND(sv))".

           Warning: If "SvCUR" is equal to "SvLEN", then "SvEND" points to
           unallocated memory.

            char*  SvEND(SV* sv)

       "sv_eq"
           Returns a boolean indicating whether the strings in the two SVs are
           identical.  Is UTF-8 and 'use bytes' aware, handles get magic, and
           will coerce its args to strings if necessary.

            I32  sv_eq(SV* sv1, SV* sv2)

       "sv_eq_flags"
           Returns a boolean indicating whether the strings in the two SVs are
           identical.  Is UTF-8 and 'use bytes' aware and coerces its args to
           strings if necessary.  If the flags has the "SV_GMAGIC" bit set, it
           handles get-magic, too.

            I32  sv_eq_flags(SV* sv1, SV* sv2, const U32 flags)

       "sv_force_normal"
           Undo various types of fakery on an SV: if the PV is a shared
           string, make a private copy; if we're a ref, stop refing; if we're
           a glob, downgrade to an "xpvmg".  See also "sv_force_normal_flags".

            void  sv_force_normal(SV *sv)

       "sv_force_normal_flags"
           Undo various types of fakery on an SV, where fakery means "more
           than" a string: if the PV is a shared string, make a private copy;
           if we're a ref, stop refing; if we're a glob, downgrade to an
           "xpvmg"; if we're a copy-on-write scalar, this is the on-write time
           when we do the copy, and is also used locally; if this is a
           vstring, drop the vstring magic.  If "SV_COW_DROP_PV" is set then a
           copy-on-write scalar drops its PV buffer (if any) and becomes
           "SvPOK_off" rather than making a copy.  (Used where this scalar is
           about to be set to some other value.)  In addition, the "flags"
           parameter gets passed to "sv_unref_flags()" when unreffing.
           "sv_force_normal" calls this function with flags set to 0.

           This function is expected to be used to signal to perl that this SV
           is about to be written to, and any extra book-keeping needs to be
           taken care of.  Hence, it croaks on read-only values.

            void  sv_force_normal_flags(SV *const sv, const U32 flags)

       "sv_free"
           Decrement an SV's reference count, and if it drops to zero, call
           "sv_clear" to invoke destructors and free up any memory used by the
           body; finally, deallocating the SV's head itself.  Normally called
           via a wrapper macro "SvREFCNT_dec".

            void  sv_free(SV *const sv)

       "SvGAMAGIC"
           Returns true if the SV has get magic or overloading.  If either is
           true then the scalar is active data, and has the potential to
           return a new value every time it is accessed.  Hence you must be
           careful to only read it once per user logical operation and work
           with that returned value.  If neither is true then the scalar's
           value cannot change unless written to.

            U32  SvGAMAGIC(SV* sv)

       "SvGETMAGIC"
           Invokes "mg_get" on an SV if it has 'get' magic.  For example, this
           will call "FETCH" on a tied variable.  This macro evaluates its
           argument more than once.

            void  SvGETMAGIC(SV* sv)

       "sv_gets"
           Get a line from the filehandle and store it into the SV, optionally
           appending to the currently-stored string.  If "append" is not 0,
           the line is appended to the SV instead of overwriting it.  "append"
           should be set to the byte offset that the appended string should
           start at in the SV (typically, "SvCUR(sv)" is a suitable choice).

            char*  sv_gets(SV *const sv, PerlIO *const fp, I32 append)

       "sv_get_backrefs"
           NOTE: "sv_get_backrefs" is experimental and may change or be
           removed without notice.

           If "sv" is the target of a weak reference then it returns the back
           references structure associated with the sv; otherwise return
           "NULL".

           When returning a non-null result the type of the return is
           relevant. If it is an AV then the elements of the AV are the weak
           reference RVs which point at this item. If it is any other type
           then the item itself is the weak reference.

           See also "Perl_sv_add_backref()", "Perl_sv_del_backref()",
           "Perl_sv_kill_backrefs()"

            SV*  sv_get_backrefs(SV *const sv)

       "SvGROW"
           Expands the character buffer in the SV so that it has room for the
           indicated number of bytes (remember to reserve space for an extra
           trailing "NUL" character).  Calls "sv_grow" to perform the
           expansion if necessary.  Returns a pointer to the character buffer.
           SV must be of type >= "SVt_PV".  One alternative is to call
           "sv_grow" if you are not sure of the type of SV.

           You might mistakenly think that "len" is the number of bytes to add
           to the existing size, but instead it is the total size "sv" should
           be.

            char *  SvGROW(SV* sv, STRLEN len)

       "sv_inc"
       "sv_inc_nomg"
           These auto-increment the value in the SV, doing string to numeric
           conversion if necessary.  They both handle operator overloading.

           They differ only in that "sv_inc" performs 'get' magic;
           "sv_inc_nomg" skips any magic.

            void  sv_inc(SV *const sv)

       "sv_insert"
           Inserts and/or replaces a string at the specified offset/length
           within the SV.  Similar to the Perl "substr()" function, with
           "littlelen" bytes starting at "little" replacing "len" bytes of the
           string in "bigstr" starting at "offset".  Handles get magic.

            void  sv_insert(SV *const bigstr, const STRLEN offset,
                            const STRLEN len, const char *const little,
                            const STRLEN littlelen)

       "sv_insert_flags"
           Same as "sv_insert", but the extra "flags" are passed to the
           "SvPV_force_flags" that applies to "bigstr".

            void  sv_insert_flags(SV *const bigstr, const STRLEN offset,
                                  const STRLEN len, const char *little,
                                  const STRLEN littlelen, const U32 flags)

       "SvIOK"
           Returns a U32 value indicating whether the SV contains an integer.

            U32  SvIOK(SV* sv)

       "SvIOK_notUV"
           Returns a boolean indicating whether the SV contains a signed
           integer.

            bool  SvIOK_notUV(SV* sv)

       "SvIOK_off"
           Unsets the IV status of an SV.

            void  SvIOK_off(SV* sv)

       "SvIOK_on"
           Tells an SV that it is an integer.

            void  SvIOK_on(SV* sv)

       "SvIOK_only"
           Tells an SV that it is an integer and disables all other "OK" bits.

            void  SvIOK_only(SV* sv)

       "SvIOK_only_UV"
           Tells an SV that it is an unsigned integer and disables all other
           "OK" bits.

            void  SvIOK_only_UV(SV* sv)

       "SvIOKp"
           Returns a U32 value indicating whether the SV contains an integer.
           Checks the private setting.  Use "SvIOK" instead.

            U32  SvIOKp(SV* sv)

       "SvIOK_UV"
           Returns a boolean indicating whether the SV contains an integer
           that must be interpreted as unsigned.  A non-negative integer whose
           value is within the range of both an IV and a UV may be flagged as
           either "SvUOK" or "SvIOK".

            bool  SvIOK_UV(SV* sv)

       "sv_isa"
           Returns a boolean indicating whether the SV is blessed into the
           specified class.

           This does not check for subtypes or method overloading. Use
           "sv_isa_sv" to verify an inheritance relationship in the same way
           as the "isa" operator by respecting any "isa()" method overloading;
           or "sv_derived_from_sv" to test directly on the actual object type.

            int  sv_isa(SV* sv, const char *const name)

       "sv_isa_sv"
           NOTE: "sv_isa_sv" is experimental and may change or be removed
           without notice.

           Returns a boolean indicating whether the SV is an object reference
           and is derived from the specified class, respecting any "isa()"
           method overloading it may have. Returns false if "sv" is not a
           reference to an object, or is not derived from the specified class.

           This is the function used to implement the behaviour of the "isa"
           operator.

           Does not invoke magic on "sv".

           Not to be confused with the older "sv_isa" function, which does not
           use an overloaded "isa()" method, nor will check subclassing.

            bool  sv_isa_sv(SV* sv, SV* namesv)

       "SvIsCOW"
           Returns a U32 value indicating whether the SV is Copy-On-Write
           (either shared hash key scalars, or full Copy On Write scalars if
           5.9.0 is configured for COW).

            U32  SvIsCOW(SV* sv)

       "SvIsCOW_shared_hash"
           Returns a boolean indicating whether the SV is Copy-On-Write shared
           hash key scalar.

            bool  SvIsCOW_shared_hash(SV* sv)

       "sv_isobject"
           Returns a boolean indicating whether the SV is an RV pointing to a
           blessed object.  If the SV is not an RV, or if the object is not
           blessed, then this will return false.

            int  sv_isobject(SV* sv)

       "SvIV"
       "SvIVx"
       "SvIV_nomg"
           These coerce the given SV to IV and return it.  The returned value
           in many circumstances will get stored in "sv"'s IV slot, but not in
           all cases.  (Use "sv_setiv" to make sure it does).

           "SvIVx" is different from the others in that it is guaranteed to
           evaluate "sv" exactly once; the others may evaluate it multiple
           times.  Only use this form if "sv" is an expression with side
           effects, otherwise use the more efficient "SvIV".

           "SvIV_nomg" is the same as "SvIV", but does not perform 'get'
           magic.

            IV  SvIV(SV* sv)

       "SvIV_set"
           Set the value of the IV pointer in sv to val.  It is possible to
           perform the same function of this macro with an lvalue assignment
           to "SvIVX".  With future Perls, however, it will be more efficient
           to use "SvIV_set" instead of the lvalue assignment to "SvIVX".

            void  SvIV_set(SV* sv, IV val)

       "SvIVX"
           Returns the raw value in the SV's IV slot, without checks or
           conversions.  Only use when you are sure "SvIOK" is true.  See also
           "SvIV".

            IV  SvIVX(SV* sv)

       "SvLEN"
           Returns the size of the string buffer in the SV, not including any
           part attributable to "SvOOK".  See "SvCUR".

            STRLEN  SvLEN(SV* sv)

       "sv_len"
           Returns the length of the string in the SV.  Handles magic and type
           coercion and sets the UTF8 flag appropriately.  See also "SvCUR",
           which gives raw access to the "xpv_cur" slot.

            STRLEN  sv_len(SV *const sv)

       "SvLEN_set"
           Set the size of the string buffer for the SV. See "SvLEN".

            void  SvLEN_set(SV* sv, STRLEN len)

       "sv_len_utf8"
           Returns the number of characters in the string in an SV, counting
           wide UTF-8 bytes as a single character.  Handles magic and type
           coercion.

            STRLEN  sv_len_utf8(SV *const sv)

       "SvLOCK"
           Arranges for a mutual exclusion lock to be obtained on "sv" if a
           suitable module has been loaded.

            void  SvLOCK(SV* sv)

       "sv_magic"
           Adds magic to an SV.  First upgrades "sv" to type "SVt_PVMG" if
           necessary, then adds a new magic item of type "how" to the head of
           the magic list.

           See "sv_magicext" (which "sv_magic" now calls) for a description of
           the handling of the "name" and "namlen" arguments.

           You need to use "sv_magicext" to add magic to "SvREADONLY" SVs and
           also to add more than one instance of the same "how".

            void  sv_magic(SV *const sv, SV *const obj, const int how,
                           const char *const name, const I32 namlen)

       "sv_magicext"
           Adds magic to an SV, upgrading it if necessary.  Applies the
           supplied "vtable" and returns a pointer to the magic added.

           Note that "sv_magicext" will allow things that "sv_magic" will not.
           In particular, you can add magic to "SvREADONLY" SVs, and add more
           than one instance of the same "how".

           If "namlen" is greater than zero then a "savepvn" copy of "name" is
           stored, if "namlen" is zero then "name" is stored as-is and - as
           another special case - if "(name && namlen == HEf_SVKEY)" then
           "name" is assumed to contain an SV* and is stored as-is with its
           "REFCNT" incremented.

           (This is now used as a subroutine by "sv_magic".)

            MAGIC *  sv_magicext(SV *const sv, SV *const obj, const int how,
                                 const MGVTBL *const vtbl,
                                 const char *const name, const I32 namlen)

       "SvMAGIC_set"
           Set the value of the MAGIC pointer in "sv" to val.  See "SvIV_set".

            void  SvMAGIC_set(SV* sv, MAGIC* val)

       "sv_mortalcopy"
           Creates a new SV which is a copy of the original SV (using
           "sv_setsv").  The new SV is marked as mortal.  It will be destroyed
           "soon", either by an explicit call to "FREETMPS", or by an implicit
           call at places such as statement boundaries.  See also
           "sv_newmortal" and "sv_2mortal".

            SV*  sv_mortalcopy(SV *const oldsv)

       "sv_mortalcopy_flags"
           Like "sv_mortalcopy", but the extra "flags" are passed to the
           "sv_setsv_flags".

            SV*  sv_mortalcopy_flags(SV *const oldsv, U32 flags)

       "sv_newmortal"
           Creates a new null SV which is mortal.  The reference count of the
           SV is set to 1.  It will be destroyed "soon", either by an explicit
           call to "FREETMPS", or by an implicit call at places such as
           statement boundaries.  See also "sv_mortalcopy" and "sv_2mortal".

            SV*  sv_newmortal()

       "SvNIOK"
           Returns a U32 value indicating whether the SV contains a number,
           integer or double.

            U32  SvNIOK(SV* sv)

       "SvNIOK_off"
           Unsets the NV/IV status of an SV.

            void  SvNIOK_off(SV* sv)

       "SvNIOKp"
           Returns a U32 value indicating whether the SV contains a number,
           integer or double.  Checks the private setting.  Use "SvNIOK"
           instead.

            U32  SvNIOKp(SV* sv)

       "SvNOK"
           Returns a U32 value indicating whether the SV contains a double.

            U32  SvNOK(SV* sv)

       "SvNOK_off"
           Unsets the NV status of an SV.

            void  SvNOK_off(SV* sv)

       "SvNOK_on"
           Tells an SV that it is a double.

            void  SvNOK_on(SV* sv)

       "SvNOK_only"
           Tells an SV that it is a double and disables all other OK bits.

            void  SvNOK_only(SV* sv)

       "SvNOKp"
           Returns a U32 value indicating whether the SV contains a double.
           Checks the private setting.  Use "SvNOK" instead.

            U32  SvNOKp(SV* sv)

       "sv_nolocking"
           "DEPRECATED!"  It is planned to remove "sv_nolocking" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Dummy routine which "locks" an SV when there is no locking module
           present.  Exists to avoid test for a "NULL" function pointer and
           because it could potentially warn under some level of strict-ness.

           "Superseded" by "sv_nosharing()".

            void  sv_nolocking(SV *sv)

       "sv_nounlocking"
           "DEPRECATED!"  It is planned to remove "sv_nounlocking" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           Dummy routine which "unlocks" an SV when there is no locking module
           present.  Exists to avoid test for a "NULL" function pointer and
           because it could potentially warn under some level of strict-ness.

           "Superseded" by "sv_nosharing()".

            void  sv_nounlocking(SV *sv)

       "SvNV"
       "SvNVx"
       "SvNV_nomg"
           These coerce the given SV to NV and return it.  The returned value
           in many circumstances will get stored in "sv"'s NV slot, but not in
           all cases.  (Use "sv_setnv" to make sure it does).

           "SvNVx" is different from the others in that it is guaranteed to
           evaluate "sv" exactly once; the others may evaluate it multiple
           times.  Only use this form if "sv" is an expression with side
           effects, otherwise use the more efficient "SvNV".

           "SvNV_nomg" is the same as "SvNV", but does not perform 'get'
           magic.

            NV  SvNV(SV* sv)

       "SvNV_set"
           Set the value of the NV pointer in "sv" to val.  See "SvIV_set".

            void  SvNV_set(SV* sv, NV val)

       "SvNVX"
           Returns the raw value in the SV's NV slot, without checks or
           conversions.  Only use when you are sure "SvNOK" is true.  See also
           "SvNV".

            NV  SvNVX(SV* sv)

       "SvOK"
           Returns a U32 value indicating whether the value is defined.  This
           is only meaningful for scalars.

            U32  SvOK(SV* sv)

       "SvOOK"
           Returns a U32 indicating whether the pointer to the string buffer
           is offset.  This hack is used internally to speed up removal of
           characters from the beginning of a "SvPV".  When "SvOOK" is true,
           then the start of the allocated string buffer is actually
           "SvOOK_offset()" bytes before "SvPVX".  This offset used to be
           stored in "SvIVX", but is now stored within the spare part of the
           buffer.

            U32  SvOOK(SV* sv)

       "SvOOK_off"
           Remove any string offset.

            void  SvOOK_off(SV * sv)

       "SvOOK_offset"
           Reads into "len" the offset from "SvPVX" back to the true start of
           the allocated buffer, which will be non-zero if "sv_chop" has been
           used to efficiently remove characters from start of the buffer.
           Implemented as a macro, which takes the address of "len", which
           must be of type "STRLEN".  Evaluates "sv" more than once.  Sets
           "len" to 0 if "SvOOK(sv)" is false.

            void  SvOOK_offset(SV*sv, STRLEN len)

       "SvPOK"
           Returns a U32 value indicating whether the SV contains a character
           string.

            U32  SvPOK(SV* sv)

       "SvPOK_off"
           Unsets the PV status of an SV.

            void  SvPOK_off(SV* sv)

       "SvPOK_on"
           Tells an SV that it is a string.

            void  SvPOK_on(SV* sv)

       "SvPOK_only"
           Tells an SV that it is a string and disables all other "OK" bits.
           Will also turn off the UTF-8 status.

            void  SvPOK_only(SV* sv)

       "SvPOK_only_UTF8"
           Tells an SV that it is a string and disables all other "OK" bits,
           and leaves the UTF-8 status as it was.

            void  SvPOK_only_UTF8(SV* sv)

       "SvPOKp"
           Returns a U32 value indicating whether the SV contains a character
           string.  Checks the private setting.  Use "SvPOK" instead.

            U32  SvPOKp(SV* sv)

       "sv_pos_b2u"
           Converts the value pointed to by "offsetp" from a count of bytes
           from the start of the string, to a count of the equivalent number
           of UTF-8 chars.  Handles magic and type coercion.

           Use "sv_pos_b2u_flags" in preference, which correctly handles
           strings longer than 2Gb.

            void  sv_pos_b2u(SV *const sv, I32 *const offsetp)

       "sv_pos_b2u_flags"
           Converts "offset" from a count of bytes from the start of the
           string, to a count of the equivalent number of UTF-8 chars.
           Handles type coercion.  "flags" is passed to "SvPV_flags", and
           usually should be "SV_GMAGIC|SV_CONST_RETURN" to handle magic.

            STRLEN  sv_pos_b2u_flags(SV *const sv, STRLEN const offset,
                                     U32 flags)

       "sv_pos_u2b"
           Converts the value pointed to by "offsetp" from a count of UTF-8
           chars from the start of the string, to a count of the equivalent
           number of bytes; if "lenp" is non-zero, it does the same to "lenp",
           but this time starting from the offset, rather than from the start
           of the string.  Handles magic and type coercion.

           Use "sv_pos_u2b_flags" in preference, which correctly handles
           strings longer than 2Gb.

            void  sv_pos_u2b(SV *const sv, I32 *const offsetp,
                             I32 *const lenp)

       "sv_pos_u2b_flags"
           Converts the offset from a count of UTF-8 chars from the start of
           the string, to a count of the equivalent number of bytes; if "lenp"
           is non-zero, it does the same to "lenp", but this time starting
           from "offset", rather than from the start of the string.  Handles
           type coercion.  "flags" is passed to "SvPV_flags", and usually
           should be "SV_GMAGIC|SV_CONST_RETURN" to handle magic.

            STRLEN  sv_pos_u2b_flags(SV *const sv, STRLEN uoffset,
                                     STRLEN *const lenp, U32 flags)

       "SvPV"
       "SvPVx"
       "SvPV_nomg"
       "SvPV_nolen"
       "SvPVx_nolen"
       "SvPV_nomg_nolen"
       "SvPV_mutable"
       "SvPV_const"
       "SvPVx_const"
       "SvPV_nolen_const"
       "SvPVx_nolen_const"
       "SvPV_nomg_const"
       "SvPV_nomg_const_nolen"
       "SvPV_flags"
       "SvPV_flags_const"
       "SvPV_flags_mutable"
       "SvPVbyte"
       "SvPVbyte_nomg"
       "SvPVbyte_nolen"
       "SvPVbytex_nolen"
       "SvPVbytex"
       "SvPVbyte_or_null"
       "SvPVbyte_or_null_nomg"
       "SvPVutf8"
       "SvPVutf8x"
       "SvPVutf8_nomg"
       "SvPVutf8_nolen"
       "SvPVutf8_or_null"
       "SvPVutf8_or_null_nomg"
           All these return a pointer to the string in "sv", or a stringified
           form of "sv" if it does not contain a string.  The SV may cache the
           stringified version becoming "SvPOK".

           This is a very basic and common operation, so there are lots of
           slightly different versions of it.

           Note that there is no guarantee that the return value of
           "SvPV(sv)", for example, is equal to "SvPVX(sv)", or that
           "SvPVX(sv)" contains valid data, or that successive calls to
           "SvPV(sv)" (or another of these forms) will return the same pointer
           value each time.  This is due to the way that things like
           overloading and Copy-On-Write are handled.  In these cases, the
           return value may point to a temporary buffer or similar.  If you
           absolutely need the "SvPVX" field to be valid (for example, if you
           intend to write to it), then see "SvPV_force".

           The differences between the forms are:

           The forms with neither "byte" nor "utf8" in their names (e.g.,
           "SvPV" or "SvPV_nolen") can expose the SV's internal string buffer.
           If that buffer consists entirely of bytes 0-255 and includes any
           bytes above 127, then you MUST consult "SvUTF8" to determine the
           actual code points the string is meant to contain. Generally
           speaking, it is probably safer to prefer "SvPVbyte", "SvPVutf8",
           and the like. See "How do I pass a Perl string to a C library?" in
           perlguts for more details.

           The forms with "flags" in their names allow you to use the "flags"
           parameter to specify to process 'get' magic (by setting the
           "SV_GMAGIC" flag) or to skip 'get' magic (by clearing it).  The
           other forms process 'get' magic, except for the ones with "nomg" in
           their names, which skip 'get' magic.

           The forms that take a "len" parameter will set that variable to the
           byte length of the resultant string (these are macros, so don't use
           &len).

           The forms with "nolen" in their names indicate they don't have a
           "len" parameter.  They should be used only when it is known that
           the PV is a C string, terminated by a NUL byte, and without
           intermediate NUL characters; or when you don't care about its
           length.

           The forms with "const" in their names return "const char *" so that
           the compiler will hopefully complain if you were to try to modify
           the contents of the string (unless you cast away const yourself).

           The other forms return a mutable pointer so that the string is
           modifiable by the caller; this is emphasized for the ones with
           "mutable" in their names.

           The forms whose name ends in "x" are the same as the corresponding
           form without the "x", but the "x" form is guaranteed to evaluate
           "sv" exactly once, with a slight loss of efficiency.  Use this if
           "sv" is an expression with side effects.

           "SvPVutf8" is like "SvPV", but converts "sv" to UTF-8 first if not
           already UTF-8.  Similiarly, the other forms with "utf8" in their
           names correspond to their respective forms without.

           "SvPVutf8_or_null" and "SvPVutf8_or_null_nomg" don't have
           corresponding non-"utf8" forms.  Instead they are like
           "SvPVutf8_nomg", but when "sv" is undef, they return "NULL".

           "SvPVbyte" is like "SvPV", but converts "sv" to byte representation
           first if currently encoded as UTF-8.  If "sv" cannot be downgraded
           from UTF-8, it croaks.  Similiarly, the other forms with "byte" in
           their names correspond to their respective forms without.

           "SvPVbyte_or_null" doesn't have a corresponding non-"byte" form.
           Instead it is like "SvPVbyte", but when "sv" is undef, it returns
           "NULL".

            char*         SvPV                 (SV* sv, STRLEN len)
            char*         SvPVx                (SV* sv, STRLEN len)
            char*         SvPV_nomg            (SV* sv, STRLEN len)
            char*         SvPV_nolen           (SV* sv)
            char*         SvPVx_nolen          (SV* sv)
            char*         SvPV_nomg_nolen      (SV* sv)
            char*         SvPV_mutable         (SV* sv, STRLEN len)
            const char*   SvPV_const           (SV* sv, STRLEN len)
            const char*   SvPVx_const          (SV* sv, STRLEN len)
            const char*   SvPV_nolen_const     (SV* sv)
            const char*   SvPVx_nolen_const    (SV* sv)
            const char*   SvPV_nomg_const      (SV* sv, STRLEN len)
            const char*   SvPV_nomg_const_nolen(SV* sv)
            char *        SvPV_flags           (SV * sv, STRLEN len,
                                                U32 flags)
            const char *  SvPV_flags_const     (SV * sv, STRLEN len,
                                                U32 flags)
            char *        SvPV_flags_mutable   (SV * sv, STRLEN len,
                                                U32 flags)
            char*         SvPVbyte             (SV* sv, STRLEN len)
            char*         SvPVbyte_nomg        (SV* sv, STRLEN len)
            char*         SvPVbyte_nolen       (SV* sv)
            char*         SvPVbytex_nolen      (SV* sv)
            char*         SvPVbytex            (SV* sv, STRLEN len)
            char*         SvPVbyte_or_null     (SV* sv, STRLEN len)
            char*         SvPVbyte_or_null_nomg(SV* sv, STRLEN len)
            char*         SvPVutf8             (SV* sv, STRLEN len)
            char*         SvPVutf8x            (SV* sv, STRLEN len)
            char*         SvPVutf8_nomg        (SV* sv, STRLEN len)
            char*         SvPVutf8_nolen       (SV* sv)
            char*         SvPVutf8_or_null     (SV* sv, STRLEN len)
            char*         SvPVutf8_or_null_nomg(SV* sv, STRLEN len)

       "SvPVbyte"
           Like "SvPV", but converts "sv" to byte representation first if
           necessary.  If the SV cannot be downgraded from UTF-8, this croaks.

            char*  SvPVbyte(SV* sv, STRLEN len)

       "SvPVbyte_force"
           Like "SvPV_force", but converts "sv" to byte representation first
           if necessary.  If the SV cannot be downgraded from UTF-8, this
           croaks.

            char*  SvPVbyte_force(SV* sv, STRLEN len)

       "SvPVbyte_nolen"
           Like "SvPV_nolen", but converts "sv" to byte representation first
           if necessary.  If the SV cannot be downgraded from UTF-8, this
           croaks.

            char*  SvPVbyte_nolen(SV* sv)

       "SvPVbyte_nomg"
           Like "SvPVbyte", but does not process get magic.

            char*  SvPVbyte_nomg(SV* sv, STRLEN len)

       "SvPVbyte_or_null"
           Like "SvPVbyte", but when "sv" is undef, returns "NULL".

            char*  SvPVbyte_or_null(SV* sv, STRLEN len)

       "SvPVbyte_or_null_nomg"
           Like "SvPVbyte_or_null", but does not process get magic.

            char*  SvPVbyte_or_null_nomg(SV* sv, STRLEN len)

       "SvPVCLEAR"
           Ensures that sv is a SVt_PV and that its SvCUR is 0, and that it is
           properly null terminated. Equivalent to sv_setpvs(""), but more
           efficient.

            char *  SvPVCLEAR(SV* sv)

       "SvPV_force"
       "SvPV_force_nolen"
       "SvPVx_force"
       "SvPV_force_nomg"
       "SvPV_force_nomg_nolen"
       "SvPV_force_mutable"
       "SvPV_force_flags"
       "SvPV_force_flags_nolen"
       "SvPV_force_flags_mutable"
       "SvPVbyte_force"
       "SvPVbytex_force"
       "SvPVutf8_force"
       "SvPVutf8x_force"
           These are like "SvPV", returning the string in the SV, but will
           force the SV into containing a string ("SvPOK"), and only a string
           ("SvPOK_only"), by hook or by crook.  You need to use one of these
           "force" routines if you are going to update the "SvPVX" directly.

           Note that coercing an arbitrary scalar into a plain PV will
           potentially strip useful data from it.  For example if the SV was
           "SvROK", then the referent will have its reference count
           decremented, and the SV itself may be converted to an "SvPOK"
           scalar with a string buffer containing a value such as
           "ARRAY(0x1234)".

           The differences between the forms are:

           The forms with "flags" in their names allow you to use the "flags"
           parameter to specify to perform 'get' magic (by setting the
           "SV_GMAGIC" flag) or to skip 'get' magic (by clearing it).  The
           other forms do perform 'get' magic, except for the ones with "nomg"
           in their names, which skip 'get' magic.

           The forms that take a "len" parameter will set that variable to the
           byte length of the resultant string (these are macros, so don't use
           &len).

           The forms with "nolen" in their names indicate they don't have a
           "len" parameter.  They should be used only when it is known that
           the PV is a C string, terminated by a NUL byte, and without
           intermediate NUL characters; or when you don't care about its
           length.

           The forms with "mutable" in their names are effectively the same as
           those without, but the name emphasizes that the string is
           modifiable by the caller, which it is in all the forms.

           "SvPVutf8_force" is like "SvPV_force", but converts "sv" to UTF-8
           first if not already UTF-8.

           "SvPVutf8x_force" is like "SvPVutf8_force", but guarantees to
           evaluate "sv" only once; use the more efficient "SvPVutf8_force"
           otherwise.

           "SvPVbyte_force" is like "SvPV_force", but converts "sv" to byte
           representation first if currently encoded as UTF-8.  If the SV
           cannot be downgraded from UTF-8, this croaks.

           "SvPVbytex_force" is like "SvPVbyte_force", but guarantees to
           evaluate "sv" only once; use the more efficient "SvPVbyte_force"
           otherwise.

            char*  SvPV_force              (SV* sv, STRLEN len)
            char*  SvPV_force_nolen        (SV* sv)
            char*  SvPVx_force             (SV* sv, STRLEN len)
            char*  SvPV_force_nomg         (SV* sv, STRLEN len)
            char*  SvPV_force_nomg_nolen   (SV * sv)
            char*  SvPV_force_mutable      (SV * sv, STRLEN len)
            char*  SvPV_force_flags        (SV * sv, STRLEN len, U32 flags)
            char*  SvPV_force_flags_nolen  (SV * sv, U32 flags)
            char*  SvPV_force_flags_mutable(SV * sv, STRLEN len, U32 flags)
            char*  SvPVbyte_force          (SV* sv, STRLEN len)
            char*  SvPVbytex_force         (SV* sv, STRLEN len)
            char*  SvPVutf8_force          (SV* sv, STRLEN len)
            char*  SvPVutf8x_force         (SV* sv, STRLEN len)

       "SvPV_free"
           Frees the PV buffer in "sv", leaving things in a precarious state,
           so should only be used as part of a larger operation

            void  SvPV_free(SV * sv)

       "sv_pvn_force_flags"
           Get a sensible string out of the SV somehow.  If "flags" has the
           "SV_GMAGIC" bit set, will "mg_get" on "sv" if appropriate, else
           not.  "sv_pvn_force" and "sv_pvn_force_nomg" are implemented in
           terms of this function.  You normally want to use the various
           wrapper macros instead: see "SvPV_force" and "SvPV_force_nomg".

            char*  sv_pvn_force_flags(SV *const sv, STRLEN *const lp,
                                      const U32 flags)

       "SvPV_renew"
           Low level micro optimization of "SvGROW".  It is generally better
           to use "SvGROW" instead.  This is because "SvPV_renew" ignores
           potential issues that "SvGROW" handles.  "sv" needs to have a real
           "PV" that is unencombered by things like COW.  Using
           "SV_CHECK_THINKFIRST" or "SV_CHECK_THINKFIRST_COW_DROP" before
           calling this should clean it up, but why not just use "SvGROW" if
           you're not sure about the provenance?

            void  SvPV_renew(SV* sv, STRLEN len)

       "SvPV_set"
           This is probably not what you want to use, you probably wanted
           "sv_usepvn_flags" or "sv_setpvn" or "sv_setpvs".

           Set the value of the PV pointer in "sv" to the Perl allocated
           "NUL"-terminated string "val".  See also "SvIV_set".

           Remember to free the previous PV buffer. There are many things to
           check.  Beware that the existing pointer may be involved in copy-
           on-write or other mischief, so do "SvOOK_off(sv)" and use
           "sv_force_normal" or "SvPV_force" (or check the "SvIsCOW" flag)
           first to make sure this modification is safe. Then finally, if it
           is not a COW, call "SvPV_free" to free the previous PV buffer.

            void  SvPV_set(SV* sv, char* val)

       "SvPVutf8"
           Like "SvPV", but converts "sv" to UTF-8 first if necessary.

            char*  SvPVutf8(SV* sv, STRLEN len)

       "SvPVutf8_force"
           Like "SvPV_force", but converts "sv" to UTF-8 first if necessary.

            char*  SvPVutf8_force(SV* sv, STRLEN len)

       "SvPVutf8_nolen"
           Like "SvPV_nolen", but converts "sv" to UTF-8 first if necessary.

            char*  SvPVutf8_nolen(SV* sv)

       "SvPVutf8_nomg"
           Like "SvPVutf8", but does not process get magic.

            char*  SvPVutf8_nomg(SV* sv, STRLEN len)

       "SvPVutf8_or_null"
           Like "SvPVutf8", but when "sv" is undef, returns "NULL".

            char*  SvPVutf8_or_null(SV* sv, STRLEN len)

       "SvPVutf8_or_null_nomg"
           Like "SvPVutf8_or_null", but does not process get magic.

            char*  SvPVutf8_or_null_nomg(SV* sv, STRLEN len)

       "SvPVX"
       "SvPVXx"
       "SvPVX_const"
       "SvPVX_mutable"
           These return a pointer to the physical string in the SV.  The SV
           must contain a string.  Prior to 5.9.3 it is not safe to execute
           these unless the SV's type >= "SVt_PV".

           These are also used to store the name of an autoloaded subroutine
           in an XS AUTOLOAD routine.  See "Autoloading with XSUBs" in
           perlguts.

           "SvPVXx" is identical to "SvPVX".

           "SvPVX_mutable" is merely a synonym for "SvPVX", but its name
           emphasizes that the string is modifiable by the caller.

           "SvPVX_const" differs in that the return value has been cast so
           that the compiler will complain if you were to try to modify the
           contents of the string, (unless you cast away const yourself).

            char*        SvPVX        (SV* sv)
            char*        SvPVXx       (SV* sv)
            const char*  SvPVX_const  (SV* sv)
            char*        SvPVX_mutable(SV* sv)

       "SvREADONLY"
           Returns true if the argument is readonly, otherwise returns false.
           Exposed to perl code via Internals::SvREADONLY().

            U32  SvREADONLY(SV* sv)

       "SvREADONLY_off"
           Mark an object as not-readonly. Exactly what this mean depends on
           the object type. Exposed to perl code via Internals::SvREADONLY().

            U32  SvREADONLY_off(SV* sv)

       "SvREADONLY_on"
           Mark an object as readonly. Exactly what this means depends on the
           object type. Exposed to perl code via Internals::SvREADONLY().

            U32  SvREADONLY_on(SV* sv)

       "sv_ref"
           Returns a SV describing what the SV passed in is a reference to.

           dst can be a SV to be set to the description or NULL, in which case
           a mortal SV is returned.

           If ob is true and the SV is blessed, the description is the class
           name, otherwise it is the type of the SV, "SCALAR", "ARRAY" etc.

            SV*  sv_ref(SV *dst, const SV *const sv, const int ob)

       "SvREFCNT"
           Returns the value of the object's reference count. Exposed to perl
           code via Internals::SvREFCNT().

            U32  SvREFCNT(SV* sv)

       "SvREFCNT_dec"
       "SvREFCNT_dec_NN"
           These decrement the reference count of the given SV.

           "SvREFCNT_dec_NN" may only be used when "sv" is known to not be
           "NULL".

            void  SvREFCNT_dec(SV *sv)

       "SvREFCNT_inc"
       "SvREFCNT_inc_NN"
       "SvREFCNT_inc_void"
       "SvREFCNT_inc_void_NN"
       "SvREFCNT_inc_simple"
       "SvREFCNT_inc_simple_NN"
       "SvREFCNT_inc_simple_void"
       "SvREFCNT_inc_simple_void_NN"
           These all increment the reference count of the given SV.  The ones
           without "void" in their names return the SV.

           "SvREFCNT_inc" is the base operation; the rest are optimizations if
           various input constraints are known to be true; hence, all can be
           replaced with "SvREFCNT_inc".

           "SvREFCNT_inc_NN" can only be used if you know "sv" is not "NULL".
           Since we don't have to check the NULLness, it's faster and smaller.

           "SvREFCNT_inc_void" can only be used if you don't need the return
           value.  The macro doesn't need to return a meaningful value.

           "SvREFCNT_inc_void_NN" can only be used if you both don't need the
           return value, and you know that "sv" is not "NULL".  The macro
           doesn't need to return a meaningful value, or check for NULLness,
           so it's smaller and faster.

           "SvREFCNT_inc_simple" can only be used with expressions without
           side effects.  Since we don't have to store a temporary value, it's
           faster.

           "SvREFCNT_inc_simple_NN" can only be used with expressions without
           side effects and you know "sv" is not "NULL".  Since we don't have
           to store a temporary value, nor check for NULLness, it's faster and
           smaller.

           "SvREFCNT_inc_simple_void" can only be used with expressions
           without side effects and you don't need the return value.

           "SvREFCNT_inc_simple_void_NN" can only be used with expressions
           without side effects, you don't need the return value, and you know
           "sv" is not "NULL".

            SV *  SvREFCNT_inc               (SV *sv)
            SV *  SvREFCNT_inc_NN            (SV *sv)
            void  SvREFCNT_inc_void          (SV *sv)
            void  SvREFCNT_inc_void_NN       (SV* sv)
            SV*   SvREFCNT_inc_simple        (SV* sv)
            SV*   SvREFCNT_inc_simple_NN     (SV* sv)
            void  SvREFCNT_inc_simple_void   (SV* sv)
            void  SvREFCNT_inc_simple_void_NN(SV* sv)

       "sv_reftype"
           Returns a string describing what the SV is a reference to.

           If ob is true and the SV is blessed, the string is the class name,
           otherwise it is the type of the SV, "SCALAR", "ARRAY" etc.

            const char*  sv_reftype(const SV *const sv, const int ob)

       "sv_replace"
           Make the first argument a copy of the second, then delete the
           original.  The target SV physically takes over ownership of the
           body of the source SV and inherits its flags; however, the target
           keeps any magic it owns, and any magic in the source is discarded.
           Note that this is a rather specialist SV copying operation; most of
           the time you'll want to use "sv_setsv" or one of its many macro
           front-ends.

            void  sv_replace(SV *const sv, SV *const nsv)

       "sv_report_used"
           Dump the contents of all SVs not yet freed (debugging aid).

            void  sv_report_used()

       "sv_reset"
           Underlying implementation for the "reset" Perl function.  Note that
           the perl-level function is vaguely deprecated.

            void  sv_reset(const char* s, HV *const stash)

       "SvROK"
           Tests if the SV is an RV.

            U32  SvROK(SV* sv)

       "SvROK_off"
           Unsets the RV status of an SV.

            void  SvROK_off(SV* sv)

       "SvROK_on"
           Tells an SV that it is an RV.

            void  SvROK_on(SV* sv)

       "SvRV"
           Dereferences an RV to return the SV.

            SV*  SvRV(SV* sv)

       "SvRV_set"
           Set the value of the RV pointer in "sv" to val.  See "SvIV_set".

            void  SvRV_set(SV* sv, SV* val)

       "sv_rvunweaken"
           Unweaken a reference: Clear the "SvWEAKREF" flag on this RV; remove
           the backreference to this RV from the array of backreferences
           associated with the target SV, increment the refcount of the
           target.  Silently ignores "undef" and warns on non-weak references.

            SV*  sv_rvunweaken(SV *const sv)

       "sv_rvweaken"
           Weaken a reference: set the "SvWEAKREF" flag on this RV; give the
           referred-to SV "PERL_MAGIC_backref" magic if it hasn't already; and
           push a back-reference to this RV onto the array of backreferences
           associated with that magic.  If the RV is magical, set magic will
           be called after the RV is cleared.  Silently ignores "undef" and
           warns on already-weak references.

            SV*  sv_rvweaken(SV *const sv)

       "sv_setiv"
       "sv_setiv_mg"
           These copy an integer into the given SV, upgrading first if
           necessary.

           They differ only in that "sv_setiv_mg" handles 'set' magic;
           "sv_setiv" does not.

            void  sv_setiv   (SV *const sv, const IV num)
            void  sv_setiv_mg(SV *const sv, const IV i)

       "SvSETMAGIC"
           Invokes "mg_set" on an SV if it has 'set' magic.  This is necessary
           after modifying a scalar, in case it is a magical variable like $|
           or a tied variable (it calls "STORE").  This macro evaluates its
           argument more than once.

            void  SvSETMAGIC(SV* sv)

       "sv_setnv"
       "sv_setnv_mg"
           These copy a double into the given SV, upgrading first if
           necessary.

           They differ only in that "sv_setnv_mg" handles 'set' magic;
           "sv_setnv" does not.

            void  sv_setnv(SV *const sv, const NV num)

       "sv_setpv"
       "sv_setpv_mg"
           These copy a string into an SV.  The string must be terminated with
           a "NUL" character, and not contain embeded "NUL"'s.

           They differ only in that:

           "sv_setpv" does not handle 'set' magic; "sv_setpv_mg" does.

            void  sv_setpv(SV *const sv, const char *const ptr)

       "sv_setpvf"
       "sv_setpvf_nocontext"
       "sv_setpvf_mg"
       "sv_setpvf_mg_nocontext"
           These work like "sv_catpvf" but copy the text into the SV instead
           of appending it.

           The differences between these are:

           "sv_setpvf" and "sv_setpvf_nocontext" do not handle 'set' magic;
           "sv_setpvf_mg" and "sv_setpvf_mg_nocontext" do.

           "sv_setpvf_nocontext" and "sv_setpvf_mg_nocontext" do not take a
           thread context ("aTHX") parameter, so are used in situations where
           the caller doesn't already have the thread context.

           NOTE: "sv_setpvf" must be explicitly called as "Perl_sv_setpvf"
           with an "aTHX_" parameter.

           NOTE: "sv_setpvf_mg" must be explicitly called as
           "Perl_sv_setpvf_mg" with an "aTHX_" parameter.

            void  Perl_sv_setpvf        (pTHX_ SV *const sv,
                                         const char *const pat, ...)
            void  sv_setpvf_nocontext   (SV *const sv, const char *const pat,
                                         ...)
            void  Perl_sv_setpvf_mg     (pTHX_ SV *const sv,
                                         const char *const pat, ...)
            void  sv_setpvf_mg_nocontext(SV *const sv, const char *const pat,
                                         ...)

       "sv_setpviv"
       "sv_setpviv_mg"
           "DEPRECATED!"  It is planned to remove "sv_setpviv" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           "DEPRECATED!"  It is planned to remove "sv_setpviv_mg" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           These copy an integer into the given SV, also updating its string
           value.

           They differ only in that "sv_setpviv_mg" performs 'set' magic;
           "sv_setpviv" skips any magic.

            void  sv_setpviv   (SV *const sv, const IV num)
            void  sv_setpviv_mg(SV *const sv, const IV iv)

       "sv_setpvn"
       "sv_setpvn_mg"
           These copy a string (possibly containing embedded "NUL" characters)
           into an SV.  The "len" parameter indicates the number of bytes to
           be copied.  If the "ptr" argument is NULL the SV will become
           undefined.

           The UTF-8 flag is not changed by these functions.  A terminating
           NUL byte is guaranteed.

           They differ only in that:

           "sv_setpvn" does not handle 'set' magic; "sv_setpvn_mg" does.

            void  sv_setpvn(SV *const sv, const char *const ptr,
                            const STRLEN len)

       "sv_setpvs"
           Like "sv_setpvn", but takes a literal string instead of a
           string/length pair.

            void  sv_setpvs(SV* sv, "literal string")

       "sv_setpvs_mg"
           Like "sv_setpvn_mg", but takes a literal string instead of a
           string/length pair.

            void  sv_setpvs_mg(SV* sv, "literal string")

       "sv_setpv_bufsize"
           Sets the SV to be a string of cur bytes length, with at least len
           bytes available. Ensures that there is a null byte at SvEND.
           Returns a char * pointer to the SvPV buffer.

            char  *  sv_setpv_bufsize(SV *const sv, const STRLEN cur,
                                      const STRLEN len)

       "sv_setref_iv"
           Copies an integer into a new SV, optionally blessing the SV.  The
           "rv" argument will be upgraded to an RV.  That RV will be modified
           to point to the new SV.  The "classname" argument indicates the
           package for the blessing.  Set "classname" to "NULL" to avoid the
           blessing.  The new SV will have a reference count of 1, and the RV
           will be returned.

            SV*  sv_setref_iv(SV *const rv, const char *const classname,
                              const IV iv)

       "sv_setref_nv"
           Copies a double into a new SV, optionally blessing the SV.  The
           "rv" argument will be upgraded to an RV.  That RV will be modified
           to point to the new SV.  The "classname" argument indicates the
           package for the blessing.  Set "classname" to "NULL" to avoid the
           blessing.  The new SV will have a reference count of 1, and the RV
           will be returned.

            SV*  sv_setref_nv(SV *const rv, const char *const classname,
                              const NV nv)

       "sv_setref_pv"
           Copies a pointer into a new SV, optionally blessing the SV.  The
           "rv" argument will be upgraded to an RV.  That RV will be modified
           to point to the new SV.  If the "pv" argument is "NULL", then
           "PL_sv_undef" will be placed into the SV.  The "classname" argument
           indicates the package for the blessing.  Set "classname" to "NULL"
           to avoid the blessing.  The new SV will have a reference count of
           1, and the RV will be returned.

           Do not use with other Perl types such as HV, AV, SV, CV, because
           those objects will become corrupted by the pointer copy process.

           Note that "sv_setref_pvn" copies the string while this copies the
           pointer.

            SV*  sv_setref_pv(SV *const rv, const char *const classname,
                              void *const pv)

       "sv_setref_pvn"
           Copies a string into a new SV, optionally blessing the SV.  The
           length of the string must be specified with "n".  The "rv" argument
           will be upgraded to an RV.  That RV will be modified to point to
           the new SV.  The "classname" argument indicates the package for the
           blessing.  Set "classname" to "NULL" to avoid the blessing.  The
           new SV will have a reference count of 1, and the RV will be
           returned.

           Note that "sv_setref_pv" copies the pointer while this copies the
           string.

            SV*  sv_setref_pvn(SV *const rv, const char *const classname,
                               const char *const pv, const STRLEN n)

       "sv_setref_pvs"
           Like "sv_setref_pvn", but takes a literal string instead of a
           string/length pair.

            SV *  sv_setref_pvs(SV *const rv, const char *const classname,
                                "literal string")

       "sv_setref_uv"
           Copies an unsigned integer into a new SV, optionally blessing the
           SV.  The "rv" argument will be upgraded to an RV.  That RV will be
           modified to point to the new SV.  The "classname" argument
           indicates the package for the blessing.  Set "classname" to "NULL"
           to avoid the blessing.  The new SV will have a reference count of
           1, and the RV will be returned.

            SV*  sv_setref_uv(SV *const rv, const char *const classname,
                              const UV uv)

       "SvSetSV"
       "SvSetMagicSV"
       "SvSetSV_nosteal"
       "SvSetMagicSV_nosteal"
           if "dsv" is the same as "ssv", these do nothing.  Otherwise they
           all call some form of "sv_setsv".  They may evaluate their
           arguments more than once.

           The only differences are:

           "SvSetMagicSV" and "SvSetMagicSV_nosteal" perform any required
           'set' magic afterwards on the destination SV; "SvSetSV" and
           "SvSetSV_nosteal" do not.

           "SvSetSV_nosteal" "SvSetMagicSV_nosteal" call a non-destructive
           version of "sv_setsv".

            void  SvSetSV(SV* dsv, SV* ssv)

       "sv_setsv"
       "sv_setsv_flags"
       "sv_setsv_mg"
       "sv_setsv_nomg"
           These copy the contents of the source SV "ssv" into the destination
           SV "dsv".  "ssv" may be destroyed if it is mortal, so don't use
           these functions if the source SV needs to be reused.  Loosely
           speaking, they perform a copy-by-value, obliterating any previous
           content of the destination.

           They differ only in that:

           "sv_setsv" calls 'get' magic on "ssv", but skips 'set' magic on
           "dsv".

           "sv_setsv_mg" calls both 'get' magic on "ssv" and 'set' magic on
           "dsv".

           "sv_setsv_nomg" skips all magic.

           "sv_setsv_flags" has a "flags" parameter which you can use to
           specify any combination of magic handling, and also you can specify
           "SV_NOSTEAL" so that the buffers of temps will not be stolen.

           You probably want to instead use one of the assortment of wrappers,
           such as "SvSetSV", "SvSetSV_nosteal", "SvSetMagicSV" and
           "SvSetMagicSV_nosteal".

           "sv_setsv_flags" is the primary function for copying scalars, and
           most other copy-ish functions and macros use it underneath.

            void  sv_setsv      (SV *dsv, SV *ssv)
            void  sv_setsv_flags(SV *dsv, SV *ssv, const I32 flags)
            void  sv_setsv_mg   (SV *const dsv, SV *const ssv)
            void  sv_setsv_nomg (SV *dsv, SV *ssv)

       "sv_setuv"
       "sv_setuv_mg"
           These copy an unsigned integer into the given SV, upgrading first
           if necessary.

           They differ only in that "sv_setuv_mg" handles 'set' magic;
           "sv_setuv" does not.

            void  sv_setuv   (SV *const sv, const UV num)
            void  sv_setuv_mg(SV *const sv, const UV u)

       "sv_set_undef"
           Equivalent to "sv_setsv(sv, &PL_sv_undef)", but more efficient.
           Doesn't handle set magic.

           The perl equivalent is "$sv = undef;". Note that it doesn't free
           any string buffer, unlike "undef $sv".

           Introduced in perl 5.25.12.

            void  sv_set_undef(SV *sv)

       "SvSHARE"
           Arranges for "sv" to be shared between threads if a suitable module
           has been loaded.

            void  SvSHARE(SV* sv)

       "SvSHARED_HASH"
           Returns the hash for "sv" created by "newSVpvn_share".

            struct hek*  SvSHARED_HASH(SV * sv)

       "SvSTASH"
           Returns the stash of the SV.

            HV*  SvSTASH(SV* sv)

       "SvSTASH_set"
           Set the value of the STASH pointer in "sv" to val.  See "SvIV_set".

            void  SvSTASH_set(SV* sv, HV* val)

       "SvTAINT"
           Taints an SV if tainting is enabled, and if some input to the
           current expression is tainted--usually a variable, but possibly
           also implicit inputs such as locale settings.  "SvTAINT" propagates
           that taintedness to the outputs of an expression in a pessimistic
           fashion; i.e., without paying attention to precisely which outputs
           are influenced by which inputs.

            void  SvTAINT(SV* sv)

       "SvTAINTED"
           Checks to see if an SV is tainted.  Returns TRUE if it is, FALSE if
           not.

            bool  SvTAINTED(SV* sv)

       "SvTAINTED_off"
           Untaints an SV.  Be very careful with this routine, as it short-
           circuits some of Perl's fundamental security features.  XS module
           authors should not use this function unless they fully understand
           all the implications of unconditionally untainting the value.
           Untainting should be done in the standard perl fashion, via a
           carefully crafted regexp, rather than directly untainting
           variables.

            void  SvTAINTED_off(SV* sv)

       "SvTAINTED_on"
           Marks an SV as tainted if tainting is enabled.

            void  SvTAINTED_on(SV* sv)

       "SvTRUE"
       "SvTRUEx"
       "SvTRUE_nomg"
       "SvTRUE_NN"
       "SvTRUE_nomg_NN"
           These return a boolean indicating whether Perl would evaluate the
           SV as true or false.  See "SvOK" for a defined/undefined test.

           As of Perl 5.32, all are guaranteed to evaluate "sv" only once.
           Prior to that release, only "SvTRUEx" guaranteed single evaluation;
           now "SvTRUEx" is identical to "SvTRUE".

           "SvTRUE_nomg" and "TRUE_nomg_NN" do not perform 'get' magic; the
           others do unless the scalar is already "SvPOK", "SvIOK", or "SvNOK"
           (the public, not the private flags).

           "SvTRUE_NN" is like "SvTRUE", but "sv" is assumed to be non-null
           (NN).  If there is a possibility that it is NULL, use plain
           "SvTRUE".

           "SvTRUE_nomg_NN" is like "SvTRUE_nomg", but "sv" is assumed to be
           non-null (NN).  If there is a possibility that it is NULL, use
           plain "SvTRUE_nomg".

            bool  SvTRUE(SV *sv)

       "SvTYPE"
           Returns the type of the SV.  See "svtype".

            svtype  SvTYPE(SV* sv)

       "SvUNLOCK"
           Releases a mutual exclusion lock on "sv" if a suitable module has
           been loaded.

            void  SvUNLOCK(SV* sv)

       "sv_unmagic"
           Removes all magic of type "type" from an SV.

            int  sv_unmagic(SV *const sv, const int type)

       "sv_unmagicext"
           Removes all magic of type "type" with the specified "vtbl" from an
           SV.

            int  sv_unmagicext(SV *const sv, const int type, MGVTBL *vtbl)

       "sv_unref"
           Unsets the RV status of the SV, and decrements the reference count
           of whatever was being referenced by the RV.  This can almost be
           thought of as a reversal of "newSVrv".  This is "sv_unref_flags"
           with the "flag" being zero.  See "SvROK_off".

            void  sv_unref(SV* sv)

       "sv_unref_flags"
           Unsets the RV status of the SV, and decrements the reference count
           of whatever was being referenced by the RV.  This can almost be
           thought of as a reversal of "newSVrv".  The "cflags" argument can
           contain "SV_IMMEDIATE_UNREF" to force the reference count to be
           decremented (otherwise the decrementing is conditional on the
           reference count being different from one or the reference being a
           readonly SV).  See "SvROK_off".

            void  sv_unref_flags(SV *const ref, const U32 flags)

       "SvUOK"
           Returns a boolean indicating whether the SV contains an integer
           that must be interpreted as unsigned.  A non-negative integer whose
           value is within the range of both an IV and a UV may be flagged as
           either "SvUOK" or "SvIOK".

            bool  SvUOK(SV* sv)

       "SvUPGRADE"
           Used to upgrade an SV to a more complex form.  Uses "sv_upgrade" to
           perform the upgrade if necessary.  See "svtype".

            void  SvUPGRADE(SV* sv, svtype type)

       "sv_upgrade"
           Upgrade an SV to a more complex form.  Generally adds a new body
           type to the SV, then copies across as much information as possible
           from the old body.  It croaks if the SV is already in a more
           complex form than requested.  You generally want to use the
           "SvUPGRADE" macro wrapper, which checks the type before calling
           "sv_upgrade", and hence does not croak.  See also "svtype".

            void  sv_upgrade(SV *const sv, svtype new_type)

       "sv_usepvn"
           Tells an SV to use "ptr" to find its string value.  Implemented by
           calling "sv_usepvn_flags" with "flags" of 0, hence does not handle
           'set' magic.  See "sv_usepvn_flags".

            void  sv_usepvn(SV* sv, char* ptr, STRLEN len)

       "sv_usepvn_flags"
           Tells an SV to use "ptr" to find its string value.  Normally the
           string is stored inside the SV, but sv_usepvn allows the SV to use
           an outside string.  "ptr" should point to memory that was allocated
           by "Newx".  It must be the start of a "Newx"-ed block of memory,
           and not a pointer to the middle of it (beware of "OOK" and copy-on-
           write), and not be from a non-"Newx" memory allocator like
           "malloc".  The string length, "len", must be supplied.  By default
           this function will "Renew" (i.e. realloc, move) the memory pointed
           to by "ptr", so that pointer should not be freed or used by the
           programmer after giving it to "sv_usepvn", and neither should any
           pointers from "behind" that pointer (e.g. ptr + 1) be used.

           If "flags & SV_SMAGIC" is true, will call "SvSETMAGIC".  If
           "flags & SV_HAS_TRAILING_NUL" is true, then "ptr[len]" must be
           "NUL", and the realloc will be skipped (i.e. the buffer is actually
           at least 1 byte longer than "len", and already meets the
           requirements for storing in "SvPVX").

            void  sv_usepvn_flags(SV *const sv, char* ptr, const STRLEN len,
                                  const U32 flags)

       "sv_usepvn_mg"
           Like "sv_usepvn", but also handles 'set' magic.

            void  sv_usepvn_mg(SV *sv, char *ptr, STRLEN len)

       "SvUTF8"
           Returns a U32 value indicating the UTF-8 status of an SV.  If
           things are set-up properly, this indicates whether or not the SV
           contains UTF-8 encoded data.  You should use this after a call to
           "SvPV" or one of its variants, in case any call to string
           overloading updates the internal flag.

           If you want to take into account the bytes pragma, use "DO_UTF8"
           instead.

            U32  SvUTF8(SV* sv)

       "sv_utf8_decode"
           If the PV of the SV is an octet sequence in Perl's extended UTF-8
           and contains a multiple-byte character, the "SvUTF8" flag is turned
           on so that it looks like a character.  If the PV contains only
           single-byte characters, the "SvUTF8" flag stays off.  Scans PV for
           validity and returns FALSE if the PV is invalid UTF-8.

            bool  sv_utf8_decode(SV *const sv)

       "sv_utf8_downgrade"
       "sv_utf8_downgrade_flags"
       "sv_utf8_downgrade_nomg"
           These attempt to convert the PV of an SV from characters to bytes.
           If the PV contains a character that cannot fit in a byte, this
           conversion will fail; in this case, "FALSE" is returned if
           "fail_ok" is true; otherwise they croak.

           They are not a general purpose Unicode to byte encoding interface:
           use the "Encode" extension for that.

           They differ only in that:

           "sv_utf8_downgrade" processes 'get' magic on "sv".

           "sv_utf8_downgrade_nomg" does not.

           "sv_utf8_downgrade_flags" has an additional "flags" parameter in
           which you can specify "SV_GMAGIC" to process 'get' magic, or leave
           it cleared to not proccess 'get' magic.

            bool  sv_utf8_downgrade      (SV *const sv, const bool fail_ok)
            bool  sv_utf8_downgrade_flags(SV *const sv, const bool fail_ok,
                                          const U32 flags)
            bool  sv_utf8_downgrade_nomg (SV *const sv, const bool fail_ok)

       "sv_utf8_encode"
           Converts the PV of an SV to UTF-8, but then turns the "SvUTF8" flag
           off so that it looks like octets again.

            void  sv_utf8_encode(SV *const sv)

       "sv_utf8_upgrade"
       "sv_utf8_upgrade_nomg"
       "sv_utf8_upgrade_flags"
       "sv_utf8_upgrade_flags_grow"
           These convert the PV of an SV to its UTF-8-encoded form.  The SV is
           forced to string form if it is not already.  They always set the
           "SvUTF8" flag to avoid future validity checks even if the whole
           string is the same in UTF-8 as not.  They return the number of
           bytes in the converted string

           The forms differ in just two ways.  The main difference is whether
           or not they perform 'get magic' on "sv".  "sv_utf8_upgrade_nomg"
           skips 'get magic'; "sv_utf8_upgrade" performs it; and
           "sv_utf8_upgrade_flags" and "sv_utf8_upgrade_flags_grow" either
           perform it (if the "SV_GMAGIC" bit is set in "flags") or don't (if
           that bit is cleared).

           The other difference is that "sv_utf8_upgrade_flags_grow" has an
           additional parameter, "extra", which allows the caller to specify
           an amount of space to be reserved as spare beyond what is needed
           for the actual conversion.  This is used when the caller knows it
           will soon be needing yet more space, and it is more efficient to
           request space from the system in a single call.  This form is
           otherwise identical to "sv_utf8_upgrade_flags".

           These are not a general purpose byte encoding to Unicode interface:
           use the Encode extension for that.

           The "SV_FORCE_UTF8_UPGRADE" flag is now ignored.

            STRLEN  sv_utf8_upgrade           (SV *sv)
            STRLEN  sv_utf8_upgrade_nomg      (SV *sv)
            STRLEN  sv_utf8_upgrade_flags     (SV *const sv, const I32 flags)
            STRLEN  sv_utf8_upgrade_flags_grow(SV *const sv, const I32 flags,
                                               STRLEN extra)

       "SvUTF8_off"
           Unsets the UTF-8 status of an SV (the data is not changed, just the
           flag).  Do not use frivolously.

            void  SvUTF8_off(SV *sv)

       "SvUTF8_on"
           Turn on the UTF-8 status of an SV (the data is not changed, just
           the flag).  Do not use frivolously.

            void  SvUTF8_on(SV *sv)

       "SvUV"
       "SvUVx"
       "SvUV_nomg"
           These coerce the given SV to UV and return it.  The returned value
           in many circumstances will get stored in "sv"'s UV slot, but not in
           all cases.  (Use "sv_setuv" to make sure it does).

           "SvUVx" is different from the others in that it is guaranteed to
           evaluate "sv" exactly once; the others may evaluate it multiple
           times.  Only use this form if "sv" is an expression with side
           effects, otherwise use the more efficient "SvUV".

           "SvUV_nomg" is the same as "SvUV", but does not perform 'get'
           magic.

            UV  SvUV(SV* sv)

       "SvUV_set"
           Set the value of the UV pointer in "sv" to val.  See "SvIV_set".

            void  SvUV_set(SV* sv, UV val)

       "SvUVX"
           Returns the raw value in the SV's UV slot, without checks or
           conversions.  Only use when you are sure "SvIOK" is true.  See also
           "SvUV".

            UV  SvUVX(SV* sv)

       "SvUVXx"
           "DEPRECATED!"  It is planned to remove "SvUVXx" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           This is an unnecessary synonym for "SvUVX"

            UV  SvUVXx(SV* sv)

       "sv_vcatpvf"
       "sv_vcatpvf_mg"
           These process their arguments like "sv_vcatpvfn" called with a non-
           null C-style variable argument list, and append the formatted
           output to "sv".

           They differ only in that "sv_vcatpvf_mg" performs 'set' magic;
           "sv_vcatpvf" skips 'set' magic.

           Both perform 'get' magic.

           They are usually accessed via their frontends "sv_catpvf" and
           "sv_catpvf_mg".

            void  sv_vcatpvf(SV *const sv, const char *const pat,
                             va_list *const args)

       "sv_vcatpvfn"
       "sv_vcatpvfn_flags"
           These process their arguments like vsprintf(3) and append the
           formatted output to an SV.  They use an array of SVs if the C-style
           variable argument list is missing ("NULL"). Argument reordering
           (using format specifiers like "%2$d" or "%*2$d") is supported only
           when using an array of SVs; using a C-style "va_list" argument list
           with a format string that uses argument reordering will yield an
           exception.

           When running with taint checks enabled, they indicate via
           "maybe_tainted" if results are untrustworthy (often due to the use
           of locales).

           They assume that "pat" has the same utf8-ness as "sv".  It's the
           caller's responsibility to ensure that this is so.

           They differ in that "sv_vcatpvfn_flags" has a "flags" parameter in
           which you can set or clear the "SV_GMAGIC" and/or SV_SMAGIC flags,
           to specify which magic to handle or not handle; whereas plain
           "sv_vcatpvfn" always specifies both 'get' and 'set' magic.

           They are usually used via one of the frontends "sv_vcatpvf" and
           "sv_vcatpvf_mg".

            void  sv_vcatpvfn      (SV *const sv, const char *const pat,
                                    const STRLEN patlen, va_list *const args,
                                    SV **const svargs, const Size_t sv_count,
                                    bool *const maybe_tainted)
            void  sv_vcatpvfn_flags(SV *const sv, const char *const pat,
                                    const STRLEN patlen, va_list *const args,
                                    SV **const svargs, const Size_t sv_count,
                                    bool *const maybe_tainted,
                                    const U32 flags)

       "SvVOK"
           Returns a boolean indicating whether the SV contains a v-string.

            bool  SvVOK(SV* sv)

       "sv_vsetpvf"
       "sv_vsetpvf_mg"
           These work like "sv_vcatpvf" but copy the text into the SV instead
           of appending it.

           They differ only in that "sv_vsetpvf_mg" performs 'set' magic;
           "sv_vsetpvf" skips all magic.

           They are usually used via their frontends, "sv_setpvf" and
           "sv_setpvf_mg".

            void  sv_vsetpvf(SV *const sv, const char *const pat,
                             va_list *const args)

       "sv_vsetpvfn"
           Works like "sv_vcatpvfn" but copies the text into the SV instead of
           appending it.

           Usually used via one of its frontends "sv_vsetpvf" and
           "sv_vsetpvf_mg".

            void  sv_vsetpvfn(SV *const sv, const char *const pat,
                              const STRLEN patlen, va_list *const args,
                              SV **const svargs, const Size_t sv_count,
                              bool *const maybe_tainted)

       "SvVSTRING_mg"
           Returns the vstring magic, or NULL if none

            MAGIC*  SvVSTRING_mg(SV * sv)

       "vnewSVpvf"
           Like "newSVpvf" but but the arguments are an encapsulated argument
           list.

            SV*  vnewSVpvf(const char *const pat, va_list *const args)


Time

       "ASCTIME_R_PROTO"
           This symbol encodes the prototype of "asctime_r".  It is zero if
           "d_asctime_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_asctime_r" is defined.

       "CTIME_R_PROTO"
           This symbol encodes the prototype of "ctime_r".  It is zero if
           "d_ctime_r" is undef, and one of the "REENTRANT_PROTO_T_ABC" macros
           of reentr.h if "d_ctime_r" is defined.

       "GMTIME_MAX"
           This symbol contains the maximum value for the "time_t" offset that
           the system function gmtime () accepts, and defaults to 0

       "GMTIME_MIN"
           This symbol contains the minimum value for the "time_t" offset that
           the system function gmtime () accepts, and defaults to 0

       "GMTIME_R_PROTO"
           This symbol encodes the prototype of "gmtime_r".  It is zero if
           "d_gmtime_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_gmtime_r" is defined.

       "HAS_ASCTIME64"
           This symbol, if defined, indicates that the "asctime64" () routine
           is available to do the 64bit variant of asctime ()

       "HAS_ASCTIME_R"
           This symbol, if defined, indicates that the "asctime_r" routine is
           available to asctime re-entrantly.

       "HAS_CTIME64"
           This symbol, if defined, indicates that the "ctime64" () routine is
           available to do the 64bit variant of ctime ()

       "HAS_CTIME_R"
           This symbol, if defined, indicates that the "ctime_r" routine is
           available to ctime re-entrantly.

       "HAS_DIFFTIME"
           This symbol, if defined, indicates that the "difftime" routine is
           available.

       "HAS_DIFFTIME64"
           This symbol, if defined, indicates that the "difftime64" () routine
           is available to do the 64bit variant of difftime ()

       "HAS_FUTIMES"
           This symbol, if defined, indicates that the "futimes" routine is
           available to change file descriptor time stamps with "struct
           timevals".

       "HAS_GETITIMER"
           This symbol, if defined, indicates that the "getitimer" routine is
           available to return interval timers.

       "HAS_GETTIMEOFDAY"
           This symbol, if defined, indicates that the "gettimeofday()" system
           call is available for a sub-second accuracy clock. Usually, the
           file sys/resource.h needs to be included (see "I_SYS_RESOURCE").
           The type "Timeval" should be used to refer to ""struct timeval"".

       "HAS_GMTIME64"
           This symbol, if defined, indicates that the "gmtime64" () routine
           is available to do the 64bit variant of gmtime ()

       "HAS_GMTIME_R"
           This symbol, if defined, indicates that the "gmtime_r" routine is
           available to gmtime re-entrantly.

       "HAS_LOCALTIME64"
           This symbol, if defined, indicates that the "localtime64" ()
           routine is available to do the 64bit variant of localtime ()

       "HAS_LOCALTIME_R"
           This symbol, if defined, indicates that the "localtime_r" routine
           is available to localtime re-entrantly.

       "HAS_MKTIME"
           This symbol, if defined, indicates that the "mktime" routine is
           available.

       "HAS_MKTIME64"
           This symbol, if defined, indicates that the "mktime64" () routine
           is available to do the 64bit variant of mktime ()

       "HAS_NANOSLEEP"
           This symbol, if defined, indicates that the "nanosleep" system call
           is available to sleep with 1E-9 sec accuracy.

       "HAS_SETITIMER"
           This symbol, if defined, indicates that the "setitimer" routine is
           available to set interval timers.

       "HAS_STRFTIME"
           This symbol, if defined, indicates that the "strftime" routine is
           available to do time formatting.

       "HAS_TIME"
           This symbol, if defined, indicates that the "time()" routine
           exists.

       "HAS_TIMEGM"
           This symbol, if defined, indicates that the "timegm" routine is
           available to do the opposite of gmtime ()

       "HAS_TIMES"
           This symbol, if defined, indicates that the "times()" routine
           exists.  Note that this became obsolete on some systems ("SUNOS"),
           which now use "getrusage()". It may be necessary to include
           sys/times.h.

       "HAS_TM_TM_GMTOFF"
           This symbol, if defined, indicates to the C program that the
           "struct tm" has a "tm_gmtoff" field.

       "HAS_TM_TM_ZONE"
           This symbol, if defined, indicates to the C program that the
           "struct tm" has a "tm_zone" field.

       "HAS_TZNAME"
           This symbol, if defined, indicates that the "tzname[]" array is
           available to access timezone names.

       "HAS_USLEEP"
           This symbol, if defined, indicates that the "usleep" routine is
           available to let the process sleep on a sub-second accuracy.

       "HAS_USLEEP_PROTO"
           This symbol, if defined, indicates that the system provides a
           prototype for the "usleep()" function.  Otherwise, it is up to the
           program to supply one.  A good guess is

            extern int usleep(useconds_t);

       "I_TIME"
           This symbol is always defined, and indicates to the C program that
           it should include time.h.

            #ifdef I_TIME
                #include <time.h>
            #endif

       "I_UTIME"
           This symbol, if defined, indicates to the C program that it should
           include utime.h.

            #ifdef I_UTIME
                #include <utime.h>
            #endif

       "LOCALTIME_MAX"
           This symbol contains the maximum value for the "time_t" offset that
           the system function localtime () accepts, and defaults to 0

       "LOCALTIME_MIN"
           This symbol contains the minimum value for the "time_t" offset that
           the system function localtime () accepts, and defaults to 0

       "LOCALTIME_R_NEEDS_TZSET"
           Many libc's "localtime_r" implementations do not call tzset, making
           them differ from "localtime()", and making timezone changes using
           $"ENV"{TZ} without explicitly calling tzset impossible. This symbol
           makes us call tzset before "localtime_r"

       "LOCALTIME_R_PROTO"
           This symbol encodes the prototype of "localtime_r".  It is zero if
           "d_localtime_r" is undef, and one of the "REENTRANT_PROTO_T_ABC"
           macros of reentr.h if "d_localtime_r" is defined.

       "L_R_TZSET"
           If "localtime_r()" needs tzset, it is defined in this define

       "mini_mktime"
           normalise "struct tm" values without the localtime() semantics (and
           overhead) of mktime().

            void  mini_mktime(struct tm *ptm)

       "my_strftime"
           strftime(), but with a different API so that the return value is a
           pointer to the formatted result (which MUST be arranged to be FREED
           BY THE CALLER).  This allows this function to increase the buffer
           size as needed, so that the caller doesn't have to worry about
           that.

           Note that yday and wday effectively are ignored by this function,
           as mini_mktime() overwrites them

           Also note that this is always executed in the underlying locale of
           the program, giving localized results.

           NOTE: "my_strftime" must be explicitly called as "Perl_my_strftime"
           with an "aTHX_" parameter.

            char *  Perl_my_strftime(pTHX_ const char *fmt, int sec, int min,
                                     int hour, int mday, int mon, int year,
                                     int wday, int yday, int isdst)


Typedef names

       "DB_Hash_t"
           This symbol contains the type of the prefix structure element in
           the db.h header file.  In older versions of DB, it was int, while
           in newer ones it is "size_t".

       "DB_Prefix_t"
           This symbol contains the type of the prefix structure element in
           the db.h header file.  In older versions of DB, it was int, while
           in newer ones it is "u_int32_t".

       "Direntry_t"
           This symbol is set to '"struct direct"' or '"struct dirent"'
           depending on whether dirent is available or not. You should use
           this pseudo type to portably declare your directory entries.

       "Fpos_t"
           This symbol holds the type used to declare file positions in libc.
           It can be "fpos_t", long, uint, etc... It may be necessary to
           include sys/types.h to get any typedef'ed information.

       "Free_t"
           This variable contains the return type of "free()".  It is usually
           void, but occasionally int.

       "Gid_t"
           This symbol holds the return type of "getgid()" and the type of
           argument to "setrgid()" and related functions.  Typically, it is
           the type of group ids in the kernel. It can be int, ushort,
           "gid_t", etc... It may be necessary to include sys/types.h to get
           any typedef'ed information.

       "Gid_t_f"
           This symbol defines the format string used for printing a "Gid_t".

       "Gid_t_sign"
           This symbol holds the signedness of a "Gid_t".  1 for unsigned, -1
           for signed.

       "Gid_t_size"
           This symbol holds the size of a "Gid_t" in bytes.

       "Groups_t"
           This symbol holds the type used for the second argument to
           "getgroups()" and "setgroups()".  Usually, this is the same as
           gidtype ("gid_t") , but sometimes it isn't.  It can be int, ushort,
           "gid_t", etc...  It may be necessary to include sys/types.h to get
           any typedef'ed information.  This is only required if you have
           "getgroups()" or "setgroups()"..

       "Malloc_t"
           This symbol is the type of pointer returned by malloc and realloc.

       "Mmap_t"
           This symbol holds the return type of the "mmap()" system call (and
           simultaneously the type of the first argument).  Usually set to
           'void *' or '"caddr_t"'.

       "Mode_t"
           This symbol holds the type used to declare file modes for systems
           calls.  It is usually "mode_t", but may be int or unsigned short.
           It may be necessary to include sys/types.h to get any typedef'ed
           information.

       "Netdb_hlen_t"
           This symbol holds the type used for the 2nd argument to
           "gethostbyaddr()".

       "Netdb_host_t"
           This symbol holds the type used for the 1st argument to
           "gethostbyaddr()".

       "Netdb_name_t"
           This symbol holds the type used for the argument to
           "gethostbyname()".

       "Netdb_net_t"
           This symbol holds the type used for the 1st argument to
           "getnetbyaddr()".

       "Off_t"
           This symbol holds the type used to declare offsets in the kernel.
           It can be int, long, "off_t", etc... It may be necessary to include
           sys/types.h to get any typedef'ed information.

       "Off_t_size"
           This symbol holds the number of bytes used by the "Off_t".

       "Pid_t"
           This symbol holds the type used to declare process ids in the
           kernel.  It can be int, uint, "pid_t", etc... It may be necessary
           to include sys/types.h to get any typedef'ed information.

       "Rand_seed_t"
           This symbol defines the type of the argument of the random seed
           function.

       "Select_fd_set_t"
           This symbol holds the type used for the 2nd, 3rd, and 4th arguments
           to select.  Usually, this is '"fd_set" *', if "HAS_FD_SET" is
           defined, and 'int *' otherwise.  This is only useful if you have
           "select()", of course.

       "Shmat_t"
           This symbol holds the return type of the "shmat()" system call.
           Usually set to 'void *' or 'char *'.

       "Signal_t"
           This symbol's value is either "void" or "int", corresponding to the
           appropriate return type of a signal handler.  Thus, you can declare
           a signal handler using ""Signal_t" (*handler)()", and define the
           handler using ""Signal_t" "handler(sig)"".

       "Size_t"
           This symbol holds the type used to declare length parameters for
           string functions.  It is usually "size_t", but may be unsigned
           long, int, etc.  It may be necessary to include sys/types.h to get
           any typedef'ed information.

       "Size_t_size"
           This symbol holds the size of a "Size_t" in bytes.

       "Sock_size_t"
           This symbol holds the type used for the size argument of various
           socket calls (just the base type, not the pointer-to).

       "SSize_t"
           This symbol holds the type used by functions that return a count of
           bytes or an error condition.  It must be a signed type.  It is
           usually "ssize_t", but may be long or int, etc.  It may be
           necessary to include sys/types.h or unistd.h to get any typedef'ed
           information.  We will pick a type such that "sizeof(SSize_t)" ==
           "sizeof(Size_t)".

       "Time_t"
           This symbol holds the type returned by "time()". It can be long, or
           "time_t" on "BSD" sites (in which case sys/types.h should be
           included).

       "Uid_t"
           This symbol holds the type used to declare user ids in the kernel.
           It can be int, ushort, "uid_t", etc... It may be necessary to
           include sys/types.h to get any typedef'ed information.

       "Uid_t_f"
           This symbol defines the format string used for printing a "Uid_t".

       "Uid_t_sign"
           This symbol holds the signedness of a "Uid_t".  1 for unsigned, -1
           for signed.

       "Uid_t_size"
           This symbol holds the size of a "Uid_t" in bytes.


Unicode Support

       "Unicode Support" in perlguts has an introduction to this API.

       See also "Character classification", "Character case changing", and
       "String Handling".  Various functions outside this section also work
       specially with Unicode.  Search for the string "utf8" in this document.

       "BOM_UTF8"
           This is a macro that evaluates to a string constant of the  UTF-8
           bytes that define the Unicode BYTE ORDER MARK (U+FEFF) for the
           platform that perl is compiled on.  This allows code to use a
           mnemonic for this character that works on both ASCII and EBCDIC
           platforms.  "sizeof(BOM_UTF8) - 1" can be used to get its length in
           bytes.

       "bytes_cmp_utf8"
           Compares the sequence of characters (stored as octets) in "b",
           "blen" with the sequence of characters (stored as UTF-8) in "u",
           "ulen".  Returns 0 if they are equal, -1 or -2 if the first string
           is less than the second string, +1 or +2 if the first string is
           greater than the second string.

           -1 or +1 is returned if the shorter string was identical to the
           start of the longer string.  -2 or +2 is returned if there was a
           difference between characters within the strings.

            int  bytes_cmp_utf8(const U8 *b, STRLEN blen, const U8 *u,
                                STRLEN ulen)

       "bytes_from_utf8"
           NOTE: "bytes_from_utf8" is experimental and may change or be
           removed without notice.

           Converts a potentially UTF-8 encoded string "s" of length *lenp
           into native byte encoding.  On input, the boolean *is_utf8p gives
           whether or not "s" is actually encoded in UTF-8.

           Unlike "utf8_to_bytes" but like "bytes_to_utf8", this is non-
           destructive of the input string.

           Do nothing if *is_utf8p is 0, or if there are code points in the
           string not expressible in native byte encoding.  In these cases,
           *is_utf8p and *lenp are unchanged, and the return value is the
           original "s".

           Otherwise, *is_utf8p is set to 0, and the return value is a pointer
           to a newly created string containing a downgraded copy of "s", and
           whose length is returned in *lenp, updated.  The new string is
           "NUL"-terminated.  The caller is responsible for arranging for the
           memory used by this string to get freed.

           Upon successful return, the number of variants in the string can be
           computed by having saved the value of *lenp before the call, and
           subtracting the after-call value of *lenp from it.

            U8*  bytes_from_utf8(const U8 *s, STRLEN *lenp, bool *is_utf8p)

       "bytes_to_utf8"
           NOTE: "bytes_to_utf8" is experimental and may change or be removed
           without notice.

           Converts a string "s" of length *lenp bytes from the native
           encoding into UTF-8.  Returns a pointer to the newly-created
           string, and sets *lenp to reflect the new length in bytes.  The
           caller is responsible for arranging for the memory used by this
           string to get freed.

           Upon successful return, the number of variants in the string can be
           computed by having saved the value of *lenp before the call, and
           subtracting it from the after-call value of *lenp.

           A "NUL" character will be written after the end of the string.

           If you want to convert to UTF-8 from encodings other than the
           native (Latin1 or EBCDIC), see "sv_recode_to_utf8"().

            U8*  bytes_to_utf8(const U8 *s, STRLEN *lenp)

       "DO_UTF8"
           Returns a bool giving whether or not the PV in "sv" is to be
           treated as being encoded in UTF-8.

           You should use this after a call to "SvPV()" or one of its
           variants, in case any call to string overloading updates the
           internal UTF-8 encoding flag.

            bool  DO_UTF8(SV* sv)

       "foldEQ_utf8"
           Returns true if the leading portions of the strings "s1" and "s2"
           (either or both of which may be in UTF-8) are the same case-
           insensitively; false otherwise.  How far into the strings to
           compare is determined by other input parameters.

           If "u1" is true, the string "s1" is assumed to be in UTF-8-encoded
           Unicode; otherwise it is assumed to be in native 8-bit encoding.
           Correspondingly for "u2" with respect to "s2".

           If the byte length "l1" is non-zero, it says how far into "s1" to
           check for fold equality.  In other words, "s1"+"l1" will be used as
           a goal to reach.  The scan will not be considered to be a match
           unless the goal is reached, and scanning won't continue past that
           goal.  Correspondingly for "l2" with respect to "s2".

           If "pe1" is non-"NULL" and the pointer it points to is not "NULL",
           that pointer is considered an end pointer to the position 1 byte
           past the maximum point in "s1" beyond which scanning will not
           continue under any circumstances.  (This routine assumes that UTF-8
           encoded input strings are not malformed; malformed input can cause
           it to read past "pe1").  This means that if both "l1" and "pe1" are
           specified, and "pe1" is less than "s1"+"l1", the match will never
           be successful because it can never get as far as its goal (and in
           fact is asserted against).  Correspondingly for "pe2" with respect
           to "s2".

           At least one of "s1" and "s2" must have a goal (at least one of
           "l1" and "l2" must be non-zero), and if both do, both have to be
           reached for a successful match.   Also, if the fold of a character
           is multiple characters, all of them must be matched (see tr21
           reference below for 'folding').

           Upon a successful match, if "pe1" is non-"NULL", it will be set to
           point to the beginning of the next character of "s1" beyond what
           was matched.  Correspondingly for "pe2" and "s2".

           For case-insensitiveness, the "casefolding" of Unicode is used
           instead of upper/lowercasing both the characters, see
           <https://www.unicode.org/unicode/reports/tr21/> (Case Mappings).

            I32  foldEQ_utf8(const char *s1, char **pe1, UV l1, bool u1,
                             const char *s2, char **pe2, UV l2, bool u2)

       "is_ascii_string"
           This is a misleadingly-named synonym for
           "is_utf8_invariant_string".  On ASCII-ish platforms, the name isn't
           misleading: the ASCII-range characters are exactly the UTF-8
           invariants.  But EBCDIC machines have more invariants than just the
           ASCII characters, so "is_utf8_invariant_string" is preferred.

            bool  is_ascii_string(const U8* const s, STRLEN len)

       "is_c9strict_utf8_string"
           Returns TRUE if the first "len" bytes of string "s" form a valid
           UTF-8-encoded string that conforms to Unicode Corrigendum #9
           <http://www.unicode.org/versions/corrigendum9.html>; otherwise it
           returns FALSE.  If "len" is 0, it will be calculated using
           strlen(s) (which means if you use this option, that "s" can't have
           embedded "NUL" characters and has to have a terminating "NUL"
           byte).  Note that all characters being ASCII constitute 'a valid
           UTF-8 string'.

           This function returns FALSE for strings containing any code points
           above the Unicode max of 0x10FFFF or surrogate code points, but
           accepts non-character code points per Corrigendum #9
           <http://www.unicode.org/versions/corrigendum9.html>.

           See also "is_utf8_invariant_string",
           "is_utf8_invariant_string_loc", "is_utf8_string",
           "is_utf8_string_flags", "is_utf8_string_loc",
           "is_utf8_string_loc_flags", "is_utf8_string_loclen",
           "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
           "is_utf8_fixed_width_buf_loc_flags",
           "is_utf8_fixed_width_buf_loclen_flags", "is_strict_utf8_string",
           "is_strict_utf8_string_loc", "is_strict_utf8_string_loclen",
           "is_c9strict_utf8_string_loc", and
           "is_c9strict_utf8_string_loclen".

            bool  is_c9strict_utf8_string(const U8 *s, STRLEN len)

       "is_c9strict_utf8_string_loc"
           Like "is_c9strict_utf8_string" but stores the location of the
           failure (in the case of "utf8ness failure") or the location
           "s"+"len" (in the case of "utf8ness success") in the "ep" pointer.

           See also "is_c9strict_utf8_string_loclen".

            bool  is_c9strict_utf8_string_loc(const U8 *s, STRLEN len,
                                              const U8 **ep)

       "is_c9strict_utf8_string_loclen"
           Like "is_c9strict_utf8_string" but stores the location of the
           failure (in the case of "utf8ness failure") or the location
           "s"+"len" (in the case of "utf8ness success") in the "ep" pointer,
           and the number of UTF-8 encoded characters in the "el" pointer.

           See also "is_c9strict_utf8_string_loc".

            bool  is_c9strict_utf8_string_loclen(const U8 *s, STRLEN len,
                                                 const U8 **ep, STRLEN *el)

       "isC9_STRICT_UTF8_CHAR"
           Evaluates to non-zero if the first few bytes of the string starting
           at "s" and looking no further than "e - 1" are well-formed UTF-8
           that represents some Unicode non-surrogate code point; otherwise it
           evaluates to 0.  If non-zero, the value gives how many bytes
           starting at "s" comprise the code point's representation.  Any
           bytes remaining before "e", but beyond the ones needed to form the
           first code point in "s", are not examined.

           The largest acceptable code point is the Unicode maximum 0x10FFFF.
           This differs from "isSTRICT_UTF8_CHAR" only in that it accepts non-
           character code points.  This corresponds to Unicode Corrigendum #9
           <http://www.unicode.org/versions/corrigendum9.html>.  which said
           that non-character code points are merely discouraged rather than
           completely forbidden in open interchange.  See "Noncharacter code
           points" in perlunicode.

           Use "isUTF8_CHAR" to check for Perl's extended UTF-8; and
           "isUTF8_CHAR_flags" for a more customized definition.

           Use "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc", and
           "is_c9strict_utf8_string_loclen" to check entire strings.

            Size_t  isC9_STRICT_UTF8_CHAR(const U8 * const s0,
                                          const U8 * const e)

       "is_invariant_string"
           This is a somewhat misleadingly-named synonym for
           "is_utf8_invariant_string".  "is_utf8_invariant_string" is
           preferred, as it indicates under what conditions the string is
           invariant.

            bool  is_invariant_string(const U8* const s, STRLEN len)

       "isSTRICT_UTF8_CHAR"
           Evaluates to non-zero if the first few bytes of the string starting
           at "s" and looking no further than "e - 1" are well-formed UTF-8
           that represents some Unicode code point completely acceptable for
           open interchange between all applications; otherwise it evaluates
           to 0.  If non-zero, the value gives how many bytes starting at "s"
           comprise the code point's representation.  Any bytes remaining
           before "e", but beyond the ones needed to form the first code point
           in "s", are not examined.

           The largest acceptable code point is the Unicode maximum 0x10FFFF,
           and must not be a surrogate nor a non-character code point.  Thus
           this excludes any code point from Perl's extended UTF-8.

           This is used to efficiently decide if the next few bytes in "s" is
           legal Unicode-acceptable UTF-8 for a single character.

           Use "isC9_STRICT_UTF8_CHAR" to use the Unicode Corrigendum #9
           <http://www.unicode.org/versions/corrigendum9.html> definition of
           allowable code points; "isUTF8_CHAR" to check for Perl's extended
           UTF-8; and "isUTF8_CHAR_flags" for a more customized definition.

           Use "is_strict_utf8_string", "is_strict_utf8_string_loc", and
           "is_strict_utf8_string_loclen" to check entire strings.

            Size_t  isSTRICT_UTF8_CHAR(const U8 * const s0,
                                       const U8 * const e)

       "is_strict_utf8_string"
           Returns TRUE if the first "len" bytes of string "s" form a valid
           UTF-8-encoded string that is fully interchangeable by any
           application using Unicode rules; otherwise it returns FALSE.  If
           "len" is 0, it will be calculated using strlen(s) (which means if
           you use this option, that "s" can't have embedded "NUL" characters
           and has to have a terminating "NUL" byte).  Note that all
           characters being ASCII constitute 'a valid UTF-8 string'.

           This function returns FALSE for strings containing any code points
           above the Unicode max of 0x10FFFF, surrogate code points, or non-
           character code points.

           See also "is_utf8_invariant_string",
           "is_utf8_invariant_string_loc", "is_utf8_string",
           "is_utf8_string_flags", "is_utf8_string_loc",
           "is_utf8_string_loc_flags", "is_utf8_string_loclen",
           "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
           "is_utf8_fixed_width_buf_loc_flags",
           "is_utf8_fixed_width_buf_loclen_flags",
           "is_strict_utf8_string_loc", "is_strict_utf8_string_loclen",
           "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc", and
           "is_c9strict_utf8_string_loclen".

            bool  is_strict_utf8_string(const U8 *s, STRLEN len)

       "is_strict_utf8_string_loc"
           Like "is_strict_utf8_string" but stores the location of the failure
           (in the case of "utf8ness failure") or the location "s"+"len" (in
           the case of "utf8ness success") in the "ep" pointer.

           See also "is_strict_utf8_string_loclen".

            bool  is_strict_utf8_string_loc(const U8 *s, STRLEN len,
                                            const U8 **ep)

       "is_strict_utf8_string_loclen"
           Like "is_strict_utf8_string" but stores the location of the failure
           (in the case of "utf8ness failure") or the location "s"+"len" (in
           the case of "utf8ness success") in the "ep" pointer, and the number
           of UTF-8 encoded characters in the "el" pointer.

           See also "is_strict_utf8_string_loc".

            bool  is_strict_utf8_string_loclen(const U8 *s, STRLEN len,
                                               const U8 **ep, STRLEN *el)

       "is_utf8_char"
           "DEPRECATED!"  It is planned to remove "is_utf8_char" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           Tests if some arbitrary number of bytes begins in a valid UTF-8
           character.  Note that an INVARIANT (i.e. ASCII on non-EBCDIC
           machines) character is a valid UTF-8 character.  The actual number
           of bytes in the UTF-8 character will be returned if it is valid,
           otherwise 0.

           This function is deprecated due to the possibility that malformed
           input could cause reading beyond the end of the input buffer.  Use
           "isUTF8_CHAR" instead.

            STRLEN  is_utf8_char(const U8 *s)

       "is_utf8_char_buf"
           This is identical to the macro "isUTF8_CHAR" in perlapi.

            STRLEN  is_utf8_char_buf(const U8 *buf, const U8 *buf_end)

       "is_utf8_fixed_width_buf_flags"
           Returns TRUE if the fixed-width buffer starting at "s" with length
           "len" is entirely valid UTF-8, subject to the restrictions given by
           "flags"; otherwise it returns FALSE.

           If "flags" is 0, any well-formed UTF-8, as extended by Perl, is
           accepted without restriction.  If the final few bytes of the buffer
           do not form a complete code point, this will return TRUE anyway,
           provided that "is_utf8_valid_partial_char_flags" returns TRUE for
           them.

           If "flags" in non-zero, it can be any combination of the
           "UTF8_DISALLOW_foo" flags accepted by "utf8n_to_uvchr", and with
           the same meanings.

           This function differs from "is_utf8_string_flags" only in that the
           latter returns FALSE if the final few bytes of the string don't
           form a complete code point.

            bool  is_utf8_fixed_width_buf_flags(const U8 * const s,
                                                STRLEN len, const U32 flags)

       "is_utf8_fixed_width_buf_loclen_flags"
           Like "is_utf8_fixed_width_buf_loc_flags" but stores the number of
           complete, valid characters found in the "el" pointer.

            bool  is_utf8_fixed_width_buf_loclen_flags(const U8 * const s,
                                                       STRLEN len,
                                                       const U8 **ep,
                                                       STRLEN *el,
                                                       const U32 flags)

       "is_utf8_fixed_width_buf_loc_flags"
           Like "is_utf8_fixed_width_buf_flags" but stores the location of the
           failure in the "ep" pointer.  If the function returns TRUE, *ep
           will point to the beginning of any partial character at the end of
           the buffer; if there is no partial character *ep will contain
           "s"+"len".

           See also "is_utf8_fixed_width_buf_loclen_flags".

            bool  is_utf8_fixed_width_buf_loc_flags(const U8 * const s,
                                                    STRLEN len, const U8 **ep,
                                                    const U32 flags)

       "is_utf8_invariant_string"
           Returns TRUE if the first "len" bytes of the string "s" are the
           same regardless of the UTF-8 encoding of the string (or UTF-EBCDIC
           encoding on EBCDIC machines); otherwise it returns FALSE.  That is,
           it returns TRUE if they are UTF-8 invariant.  On ASCII-ish
           machines, all the ASCII characters and only the ASCII characters
           fit this definition.  On EBCDIC machines, the ASCII-range
           characters are invariant, but so also are the C1 controls.

           If "len" is 0, it will be calculated using strlen(s), (which means
           if you use this option, that "s" can't have embedded "NUL"
           characters and has to have a terminating "NUL" byte).

           See also "is_utf8_string", "is_utf8_string_flags",
           "is_utf8_string_loc", "is_utf8_string_loc_flags",
           "is_utf8_string_loclen", "is_utf8_string_loclen_flags",
           "is_utf8_fixed_width_buf_flags",
           "is_utf8_fixed_width_buf_loc_flags",
           "is_utf8_fixed_width_buf_loclen_flags", "is_strict_utf8_string",
           "is_strict_utf8_string_loc", "is_strict_utf8_string_loclen",
           "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc", and
           "is_c9strict_utf8_string_loclen".

            bool  is_utf8_invariant_string(const U8* const s, STRLEN len)

       "is_utf8_invariant_string_loc"
           Like "is_utf8_invariant_string" but upon failure, stores the
           location of the first UTF-8 variant character in the "ep" pointer;
           if all characters are UTF-8 invariant, this function does not
           change the contents of *ep.

            bool  is_utf8_invariant_string_loc(const U8* const s, STRLEN len,
                                               const U8 ** ep)

       "is_utf8_string"
           Returns TRUE if the first "len" bytes of string "s" form a valid
           Perl-extended-UTF-8 string; returns FALSE otherwise.  If "len" is
           0, it will be calculated using strlen(s) (which means if you use
           this option, that "s" can't have embedded "NUL" characters and has
           to have a terminating "NUL" byte).  Note that all characters being
           ASCII constitute 'a valid UTF-8 string'.

           This function considers Perl's extended UTF-8 to be valid.  That
           means that code points above Unicode, surrogates, and non-character
           code points are considered valid by this function.  Use
           "is_strict_utf8_string", "is_c9strict_utf8_string", or
           "is_utf8_string_flags" to restrict what code points are considered
           valid.

           See also "is_utf8_invariant_string",
           "is_utf8_invariant_string_loc", "is_utf8_string_loc",
           "is_utf8_string_loclen", "is_utf8_fixed_width_buf_flags",
           "is_utf8_fixed_width_buf_loc_flags",
           "is_utf8_fixed_width_buf_loclen_flags",

            bool  is_utf8_string(const U8 *s, STRLEN len)

       "is_utf8_string_flags"
           Returns TRUE if the first "len" bytes of string "s" form a valid
           UTF-8 string, subject to the restrictions imposed by "flags";
           returns FALSE otherwise.  If "len" is 0, it will be calculated
           using strlen(s) (which means if you use this option, that "s" can't
           have embedded "NUL" characters and has to have a terminating "NUL"
           byte).  Note that all characters being ASCII constitute 'a valid
           UTF-8 string'.

           If "flags" is 0, this gives the same results as "is_utf8_string";
           if "flags" is "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", this gives the
           same results as "is_strict_utf8_string"; and if "flags" is
           "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE", this gives the same results
           as "is_c9strict_utf8_string".  Otherwise "flags" may be any
           combination of the "UTF8_DISALLOW_foo" flags understood by
           "utf8n_to_uvchr", with the same meanings.

           See also "is_utf8_invariant_string",
           "is_utf8_invariant_string_loc", "is_utf8_string",
           "is_utf8_string_loc", "is_utf8_string_loc_flags",
           "is_utf8_string_loclen", "is_utf8_string_loclen_flags",
           "is_utf8_fixed_width_buf_flags",
           "is_utf8_fixed_width_buf_loc_flags",
           "is_utf8_fixed_width_buf_loclen_flags", "is_strict_utf8_string",
           "is_strict_utf8_string_loc", "is_strict_utf8_string_loclen",
           "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc", and
           "is_c9strict_utf8_string_loclen".

            bool  is_utf8_string_flags(const U8 *s, STRLEN len,
                                       const U32 flags)

       "is_utf8_string_loc"
           Like "is_utf8_string" but stores the location of the failure (in
           the case of "utf8ness failure") or the location "s"+"len" (in the
           case of "utf8ness success") in the "ep" pointer.

           See also "is_utf8_string_loclen".

            bool  is_utf8_string_loc(const U8 *s, const STRLEN len,
                                     const U8 **ep)

       "is_utf8_string_loclen"
           Like "is_utf8_string" but stores the location of the failure (in
           the case of "utf8ness failure") or the location "s"+"len" (in the
           case of "utf8ness success") in the "ep" pointer, and the number of
           UTF-8 encoded characters in the "el" pointer.

           See also "is_utf8_string_loc".

            bool  is_utf8_string_loclen(const U8 *s, STRLEN len,
                                        const U8 **ep, STRLEN *el)

       "is_utf8_string_loclen_flags"
           Like "is_utf8_string_flags" but stores the location of the failure
           (in the case of "utf8ness failure") or the location "s"+"len" (in
           the case of "utf8ness success") in the "ep" pointer, and the number
           of UTF-8 encoded characters in the "el" pointer.

           See also "is_utf8_string_loc_flags".

            bool  is_utf8_string_loclen_flags(const U8 *s, STRLEN len,
                                              const U8 **ep, STRLEN *el,
                                              const U32 flags)

       "is_utf8_string_loc_flags"
           Like "is_utf8_string_flags" but stores the location of the failure
           (in the case of "utf8ness failure") or the location "s"+"len" (in
           the case of "utf8ness success") in the "ep" pointer.

           See also "is_utf8_string_loclen_flags".

            bool  is_utf8_string_loc_flags(const U8 *s, STRLEN len,
                                           const U8 **ep, const U32 flags)

       "is_utf8_valid_partial_char"
           Returns 0 if the sequence of bytes starting at "s" and looking no
           further than "e - 1" is the UTF-8 encoding, as extended by Perl,
           for one or more code points.  Otherwise, it returns 1 if there
           exists at least one non-empty sequence of bytes that when appended
           to sequence "s", starting at position "e" causes the entire
           sequence to be the well-formed UTF-8 of some code point; otherwise
           returns 0.

           In other words this returns TRUE if "s" points to a partial
           UTF-8-encoded code point.

           This is useful when a fixed-length buffer is being tested for being
           well-formed UTF-8, but the final few bytes in it don't comprise a
           full character; that is, it is split somewhere in the middle of the
           final code point's UTF-8 representation.  (Presumably when the
           buffer is refreshed with the next chunk of data, the new first
           bytes will complete the partial code point.)   This function is
           used to verify that the final bytes in the current buffer are in
           fact the legal beginning of some code point, so that if they
           aren't, the failure can be signalled without having to wait for the
           next read.

            bool  is_utf8_valid_partial_char(const U8 * const s,
                                             const U8 * const e)

       "is_utf8_valid_partial_char_flags"
           Like "is_utf8_valid_partial_char", it returns a boolean giving
           whether or not the input is a valid UTF-8 encoded partial
           character, but it takes an extra parameter, "flags", which can
           further restrict which code points are considered valid.

           If "flags" is 0, this behaves identically to
           "is_utf8_valid_partial_char".  Otherwise "flags" can be any
           combination of the "UTF8_DISALLOW_foo" flags accepted by
           "utf8n_to_uvchr".  If there is any sequence of bytes that can
           complete the input partial character in such a way that a non-
           prohibited character is formed, the function returns TRUE;
           otherwise FALSE.  Non character code points cannot be determined
           based on partial character input.  But many  of the other possible
           excluded types can be determined from just the first one or two
           bytes.

            bool  is_utf8_valid_partial_char_flags(const U8 * const s,
                                                   const U8 * const e,
                                                   const U32 flags)

       "isUTF8_CHAR"
           Evaluates to non-zero if the first few bytes of the string starting
           at "s" and looking no further than "e - 1" are well-formed UTF-8,
           as extended by Perl, that represents some code point; otherwise it
           evaluates to 0.  If non-zero, the value gives how many bytes
           starting at "s" comprise the code point's representation.  Any
           bytes remaining before "e", but beyond the ones needed to form the
           first code point in "s", are not examined.

           The code point can be any that will fit in an IV on this machine,
           using Perl's extension to official UTF-8 to represent those higher
           than the Unicode maximum of 0x10FFFF.  That means that this macro
           is used to efficiently decide if the next few bytes in "s" is legal
           UTF-8 for a single character.

           Use "isSTRICT_UTF8_CHAR" to restrict the acceptable code points to
           those defined by Unicode to be fully interchangeable across
           applications; "isC9_STRICT_UTF8_CHAR" to use the Unicode
           Corrigendum #9 <http://www.unicode.org/versions/corrigendum9.html>
           definition of allowable code points; and "isUTF8_CHAR_flags" for a
           more customized definition.

           Use "is_utf8_string", "is_utf8_string_loc", and
           "is_utf8_string_loclen" to check entire strings.

           Note also that a UTF-8 "invariant" character (i.e. ASCII on non-
           EBCDIC machines) is a valid UTF-8 character.

            Size_t  isUTF8_CHAR(const U8 * const s0, const U8 * const e)

       "isUTF8_CHAR_flags"
           Evaluates to non-zero if the first few bytes of the string starting
           at "s" and looking no further than "e - 1" are well-formed UTF-8,
           as extended by Perl, that represents some code point, subject to
           the restrictions given by "flags"; otherwise it evaluates to 0.  If
           non-zero, the value gives how many bytes starting at "s" comprise
           the code point's representation.  Any bytes remaining before "e",
           but beyond the ones needed to form the first code point in "s", are
           not examined.

           If "flags" is 0, this gives the same results as "isUTF8_CHAR"; if
           "flags" is "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", this gives the same
           results as "isSTRICT_UTF8_CHAR"; and if "flags" is
           "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE", this gives the same results
           as "isC9_STRICT_UTF8_CHAR".  Otherwise "flags" may be any
           combination of the "UTF8_DISALLOW_foo" flags understood by
           "utf8n_to_uvchr", with the same meanings.

           The three alternative macros are for the most commonly needed
           validations; they are likely to run somewhat faster than this more
           general one, as they can be inlined into your code.

           Use "is_utf8_string_flags", "is_utf8_string_loc_flags", and
           "is_utf8_string_loclen_flags" to check entire strings.

            STRLEN  isUTF8_CHAR_flags(const U8 *s, const U8 *e,
                                      const U32 flags)

       "LATIN1_TO_NATIVE"
           Returns the native  equivalent of the input Latin-1 code point
           (including ASCII and control characters) given by "ch".  Thus,
           "LATIN1_TO_NATIVE(66)" on EBCDIC platforms returns 194.  These each
           represent the character "B" on their respective platforms.  On
           ASCII platforms no conversion is needed, so this macro expands to
           just its input, adding no time nor space requirements to the
           implementation.

           For conversion of code points potentially larger than will fit in a
           character, use "UNI_TO_NATIVE".

            U8  LATIN1_TO_NATIVE(U8 ch)

       "NATIVE_TO_LATIN1"
           Returns the Latin-1 (including ASCII and control characters)
           equivalent of the input native code point given by "ch".  Thus,
           "NATIVE_TO_LATIN1(193)" on EBCDIC platforms returns 65.  These each
           represent the character "A" on their respective platforms.  On
           ASCII platforms no conversion is needed, so this macro expands to
           just its input, adding no time nor space requirements to the
           implementation.

           For conversion of code points potentially larger than will fit in a
           character, use "NATIVE_TO_UNI".

            U8  NATIVE_TO_LATIN1(U8 ch)

       "NATIVE_TO_UNI"
           Returns the Unicode  equivalent of the input native code point
           given by "ch".  Thus, "NATIVE_TO_UNI(195)" on EBCDIC platforms
           returns 67.  These each represent the character "C" on their
           respective platforms.  On ASCII platforms no conversion is needed,
           so this macro expands to just its input, adding no time nor space
           requirements to the implementation.

            UV  NATIVE_TO_UNI(UV ch)

       "pad_compname_type"
           "DEPRECATED!"  It is planned to remove "pad_compname_type" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           Looks up the type of the lexical variable at position "po" in the
           currently-compiling pad.  If the variable is typed, the stash of
           the class to which it is typed is returned.  If not, "NULL" is
           returned.

           Use ""PAD_COMPNAME_TYPE"" in perlintern instead.

            HV*  pad_compname_type(const PADOFFSET po)

       "pv_uni_display"
           Build to the scalar "dsv" a displayable version of the UTF-8
           encoded string "spv", length "len", the displayable version being
           at most "pvlim" bytes long (if longer, the rest is truncated and
           "..." will be appended).

           The "flags" argument can have "UNI_DISPLAY_ISPRINT" set to display
           "isPRINT()"able characters as themselves, "UNI_DISPLAY_BACKSLASH"
           to display the "\\[nrfta\\]" as the backslashed versions (like
           "\n") ("UNI_DISPLAY_BACKSLASH" is preferred over
           "UNI_DISPLAY_ISPRINT" for "\\").  "UNI_DISPLAY_QQ" (and its alias
           "UNI_DISPLAY_REGEX") have both "UNI_DISPLAY_BACKSLASH" and
           "UNI_DISPLAY_ISPRINT" turned on.

           Additionally, there is now "UNI_DISPLAY_BACKSPACE" which allows
           "\b" for a backspace, but only when "UNI_DISPLAY_BACKSLASH" also is
           set.

           The pointer to the PV of the "dsv" is returned.

           See also "sv_uni_display".

            char*  pv_uni_display(SV *dsv, const U8 *spv, STRLEN len,
                                  STRLEN pvlim, UV flags)

       "REPLACEMENT_CHARACTER_UTF8"
           This is a macro that evaluates to a string constant of the  UTF-8
           bytes that define the Unicode REPLACEMENT CHARACTER (U+FFFD) for
           the platform that perl is compiled on.  This allows code to use a
           mnemonic for this character that works on both ASCII and EBCDIC
           platforms.  "sizeof(REPLACEMENT_CHARACTER_UTF8) - 1" can be used to
           get its length in bytes.

       "sv_cat_decode"
           "encoding" is assumed to be an "Encode" object, the PV of "ssv" is
           assumed to be octets in that encoding and decoding the input starts
           from the position which "(PV + *offset)" pointed to.  "dsv" will be
           concatenated with the decoded UTF-8 string from "ssv".  Decoding
           will terminate when the string "tstr" appears in decoding output or
           the input ends on the PV of "ssv".  The value which "offset" points
           will be modified to the last input position on "ssv".

           Returns TRUE if the terminator was found, else returns FALSE.

            bool  sv_cat_decode(SV* dsv, SV *encoding, SV *ssv, int *offset,
                                char* tstr, int tlen)

       "sv_recode_to_utf8"
           "encoding" is assumed to be an "Encode" object, on entry the PV of
           "sv" is assumed to be octets in that encoding, and "sv" will be
           converted into Unicode (and UTF-8).

           If "sv" already is UTF-8 (or if it is not "POK"), or if "encoding"
           is not a reference, nothing is done to "sv".  If "encoding" is not
           an "Encode::XS" Encoding object, bad things will happen.  (See
           cpan/Encode/encoding.pm and Encode.)

           The PV of "sv" is returned.

            char*  sv_recode_to_utf8(SV* sv, SV *encoding)

       "sv_uni_display"
           Build to the scalar "dsv" a displayable version of the scalar "sv",
           the displayable version being at most "pvlim" bytes long (if
           longer, the rest is truncated and "..." will be appended).

           The "flags" argument is as in "pv_uni_display"().

           The pointer to the PV of the "dsv" is returned.

            char*  sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim, UV flags)

       "UNICODE_REPLACEMENT"
           Evaluates to 0xFFFD, the code point of the Unicode REPLACEMENT
           CHARACTER

       "UNI_TO_NATIVE"
           Returns the native  equivalent of the input Unicode code point
           given by "ch".  Thus, "UNI_TO_NATIVE(68)" on EBCDIC platforms
           returns 196.  These each represent the character "D" on their
           respective platforms.  On ASCII platforms no conversion is needed,
           so this macro expands to just its input, adding no time nor space
           requirements to the implementation.

            UV  UNI_TO_NATIVE(UV ch)

       "utf8n_to_uvchr"
           THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
           CIRCUMSTANCES.  Most code should use "utf8_to_uvchr_buf"() rather
           than call this directly.

           Bottom level UTF-8 decode routine.  Returns the native code point
           value of the first character in the string "s", which is assumed to
           be in UTF-8 (or UTF-EBCDIC) encoding, and no longer than "curlen"
           bytes; *retlen (if "retlen" isn't NULL) will be set to the length,
           in bytes, of that character.

           The value of "flags" determines the behavior when "s" does not
           point to a well-formed UTF-8 character.  If "flags" is 0,
           encountering a malformation causes zero to be returned and *retlen
           is set so that ("s" + *retlen) is the next possible position in "s"
           that could begin a non-malformed character.  Also, if UTF-8
           warnings haven't been lexically disabled, a warning is raised.
           Some UTF-8 input sequences may contain multiple malformations.
           This function tries to find every possible one in each call, so
           multiple warnings can be raised for the same sequence.

           Various ALLOW flags can be set in "flags" to allow (and not warn
           on) individual types of malformations, such as the sequence being
           overlong (that is, when there is a shorter sequence that can
           express the same code point; overlong sequences are expressly
           forbidden in the UTF-8 standard due to potential security issues).
           Another malformation example is the first byte of a character not
           being a legal first byte.  See utf8.h for the list of such flags.
           Even if allowed, this function generally returns the Unicode
           REPLACEMENT CHARACTER when it encounters a malformation.  There are
           flags in utf8.h to override this behavior for the overlong
           malformations, but don't do that except for very specialized
           purposes.

           The "UTF8_CHECK_ONLY" flag overrides the behavior when a non-
           allowed (by other flags) malformation is found.  If this flag is
           set, the routine assumes that the caller will raise a warning, and
           this function will silently just set "retlen" to "-1" (cast to
           "STRLEN") and return zero.

           Note that this API requires disambiguation between successful
           decoding a "NUL" character, and an error return (unless the
           "UTF8_CHECK_ONLY" flag is set), as in both cases, 0 is returned,
           and, depending on the malformation, "retlen" may be set to 1.  To
           disambiguate, upon a zero return, see if the first byte of "s" is 0
           as well.  If so, the input was a "NUL"; if not, the input had an
           error.  Or you can use "utf8n_to_uvchr_error".

           Certain code points are considered problematic.  These are Unicode
           surrogates, Unicode non-characters, and code points above the
           Unicode maximum of 0x10FFFF.  By default these are considered
           regular code points, but certain situations warrant special
           handling for them, which can be specified using the "flags"
           parameter.  If "flags" contains
           "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", all three classes are treated
           as malformations and handled as such.  The flags
           "UTF8_DISALLOW_SURROGATE", "UTF8_DISALLOW_NONCHAR", and
           "UTF8_DISALLOW_SUPER" (meaning above the legal Unicode maximum) can
           be set to disallow these categories individually.
           "UTF8_DISALLOW_ILLEGAL_INTERCHANGE" restricts the allowed inputs to
           the strict UTF-8 traditionally defined by Unicode.  Use
           "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE" to use the strictness
           definition given by Unicode Corrigendum #9
           <https://www.unicode.org/versions/corrigendum9.html>.  The
           difference between traditional strictness and C9 strictness is that
           the latter does not forbid non-character code points.  (They are
           still discouraged, however.)  For more discussion see "Noncharacter
           code points" in perlunicode.

           The flags "UTF8_WARN_ILLEGAL_INTERCHANGE",
           "UTF8_WARN_ILLEGAL_C9_INTERCHANGE", "UTF8_WARN_SURROGATE",
           "UTF8_WARN_NONCHAR", and "UTF8_WARN_SUPER" will cause warning
           messages to be raised for their respective categories, but
           otherwise the code points are considered valid (not malformations).
           To get a category to both be treated as a malformation and raise a
           warning, specify both the WARN and DISALLOW flags.  (But note that
           warnings are not raised if lexically disabled nor if
           "UTF8_CHECK_ONLY" is also specified.)

           Extremely high code points were never specified in any standard,
           and require an extension to UTF-8 to express, which Perl does.  It
           is likely that programs written in something other than Perl would
           not be able to read files that contain these; nor would Perl
           understand files written by something that uses a different
           extension.  For these reasons, there is a separate set of flags
           that can warn and/or disallow these extremely high code points,
           even if other above-Unicode ones are accepted.  They are the
           "UTF8_WARN_PERL_EXTENDED" and "UTF8_DISALLOW_PERL_EXTENDED" flags.
           For more information see "UTF8_GOT_PERL_EXTENDED".  Of course
           "UTF8_DISALLOW_SUPER" will treat all above-Unicode code points,
           including these, as malformations.  (Note that the Unicode standard
           considers anything above 0x10FFFF to be illegal, but there are
           standards predating it that allow up to 0x7FFF_FFFF (2**31 -1))

           A somewhat misleadingly named synonym for "UTF8_WARN_PERL_EXTENDED"
           is retained for backward compatibility: "UTF8_WARN_ABOVE_31_BIT".
           Similarly, "UTF8_DISALLOW_ABOVE_31_BIT" is usable instead of the
           more accurately named "UTF8_DISALLOW_PERL_EXTENDED".  The names are
           misleading because these flags can apply to code points that
           actually do fit in 31 bits.  This happens on EBCDIC platforms, and
           sometimes when the overlong malformation is also present.  The new
           names accurately describe the situation in all cases.

           All other code points corresponding to Unicode characters,
           including private use and those yet to be assigned, are never
           considered malformed and never warn.

            UV  utf8n_to_uvchr(const U8 *s, STRLEN curlen, STRLEN *retlen,
                               const U32 flags)

       "utf8n_to_uvchr_error"
           THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
           CIRCUMSTANCES.  Most code should use "utf8_to_uvchr_buf"() rather
           than call this directly.

           This function is for code that needs to know what the precise
           malformation(s) are when an error is found.  If you also need to
           know the generated warning messages, use "utf8n_to_uvchr_msgs"()
           instead.

           It is like "utf8n_to_uvchr" but it takes an extra parameter placed
           after all the others, "errors".  If this parameter is 0, this
           function behaves identically to "utf8n_to_uvchr".  Otherwise,
           "errors" should be a pointer to a "U32" variable, which this
           function sets to indicate any errors found.  Upon return, if
           *errors is 0, there were no errors found.  Otherwise, *errors is
           the bit-wise "OR" of the bits described in the list below.  Some of
           these bits will be set if a malformation is found, even if the
           input "flags" parameter indicates that the given malformation is
           allowed; those exceptions are noted:

           "UTF8_GOT_PERL_EXTENDED"
               The input sequence is not standard UTF-8, but a Perl extension.
               This bit is set only if the input "flags" parameter contains
               either the "UTF8_DISALLOW_PERL_EXTENDED" or the
               "UTF8_WARN_PERL_EXTENDED" flags.

               Code points above 0x7FFF_FFFF (2**31 - 1) were never specified
               in any standard, and so some extension must be used to express
               them.  Perl uses a natural extension to UTF-8 to represent the
               ones up to 2**36-1, and invented a further extension to
               represent even higher ones, so that any code point that fits in
               a 64-bit word can be represented.  Text using these extensions
               is not likely to be portable to non-Perl code.  We lump both of
               these extensions together and refer to them as Perl extended
               UTF-8.  There exist other extensions that people have invented,
               incompatible with Perl's.

               On EBCDIC platforms starting in Perl v5.24, the Perl extension
               for representing extremely high code points kicks in at
               0x3FFF_FFFF (2**30 -1), which is lower than on ASCII.  Prior to
               that, code points 2**31 and higher were simply unrepresentable,
               and a different, incompatible method was used to represent code
               points between 2**30 and 2**31 - 1.

               On both platforms, ASCII and EBCDIC, "UTF8_GOT_PERL_EXTENDED"
               is set if Perl extended UTF-8 is used.

               In earlier Perls, this bit was named "UTF8_GOT_ABOVE_31_BIT",
               which you still may use for backward compatibility.  That name
               is misleading, as this flag may be set when the code point
               actually does fit in 31 bits.  This happens on EBCDIC
               platforms, and sometimes when the overlong malformation is also
               present.  The new name accurately describes the situation in
               all cases.

           "UTF8_GOT_CONTINUATION"
               The input sequence was malformed in that the first byte was a
               UTF-8 continuation byte.

           "UTF8_GOT_EMPTY"
               The input "curlen" parameter was 0.

           "UTF8_GOT_LONG"
               The input sequence was malformed in that there is some other
               sequence that evaluates to the same code point, but that
               sequence is shorter than this one.

               Until Unicode 3.1, it was legal for programs to accept this
               malformation, but it was discovered that this created security
               issues.

           "UTF8_GOT_NONCHAR"
               The code point represented by the input UTF-8 sequence is for a
               Unicode non-character code point.  This bit is set only if the
               input "flags" parameter contains either the
               "UTF8_DISALLOW_NONCHAR" or the "UTF8_WARN_NONCHAR" flags.

           "UTF8_GOT_NON_CONTINUATION"
               The input sequence was malformed in that a non-continuation
               type byte was found in a position where only a continuation
               type one should be.  See also "UTF8_GOT_SHORT".

           "UTF8_GOT_OVERFLOW"
               The input sequence was malformed in that it is for a code point
               that is not representable in the number of bits available in an
               IV on the current platform.

           "UTF8_GOT_SHORT"
               The input sequence was malformed in that "curlen" is smaller
               than required for a complete sequence.  In other words, the
               input is for a partial character sequence.

               "UTF8_GOT_SHORT" and "UTF8_GOT_NON_CONTINUATION" both indicate
               a too short sequence.  The difference is that
               "UTF8_GOT_NON_CONTINUATION" indicates always that there is an
               error, while "UTF8_GOT_SHORT" means that an incomplete sequence
               was looked at.   If no other flags are present, it means that
               the sequence was valid as far as it went.  Depending on the
               application, this could mean one of three things:

               o   The "curlen" length parameter passed in was too small, and
                   the function was prevented from examining all the necessary
                   bytes.

               o   The buffer being looked at is based on reading data, and
                   the data received so far stopped in the middle of a
                   character, so that the next read will read the remainder of
                   this character.  (It is up to the caller to deal with the
                   split bytes somehow.)

               o   This is a real error, and the partial sequence is all we're
                   going to get.

           "UTF8_GOT_SUPER"
               The input sequence was malformed in that it is for a non-
               Unicode code point; that is, one above the legal Unicode
               maximum.  This bit is set only if the input "flags" parameter
               contains either the "UTF8_DISALLOW_SUPER" or the
               "UTF8_WARN_SUPER" flags.

           "UTF8_GOT_SURROGATE"
               The input sequence was malformed in that it is for a -Unicode
               UTF-16 surrogate code point.  This bit is set only if the input
               "flags" parameter contains either the "UTF8_DISALLOW_SURROGATE"
               or the "UTF8_WARN_SURROGATE" flags.

           To do your own error handling, call this function with the
           "UTF8_CHECK_ONLY" flag to suppress any warnings, and then examine
           the *errors return.

            UV  utf8n_to_uvchr_error(const U8 *s, STRLEN curlen,
                                     STRLEN *retlen, const U32 flags,
                                     U32 * errors)

       "utf8n_to_uvchr_msgs"
           THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
           CIRCUMSTANCES.  Most code should use "utf8_to_uvchr_buf"() rather
           than call this directly.

           This function is for code that needs to know what the precise
           malformation(s) are when an error is found, and wants the
           corresponding warning and/or error messages to be returned to the
           caller rather than be displayed.  All messages that would have been
           displayed if all lexical warnings are enabled will be returned.

           It is just like "utf8n_to_uvchr_error" but it takes an extra
           parameter placed after all the others, "msgs".  If this parameter
           is 0, this function behaves identically to "utf8n_to_uvchr_error".
           Otherwise, "msgs" should be a pointer to an "AV *" variable, in
           which this function creates a new AV to contain any appropriate
           messages.  The elements of the array are ordered so that the first
           message that would have been displayed is in the 0th element, and
           so on.  Each element is a hash with three key-value pairs, as
           follows:

           "text"
               The text of the message as a "SVpv".

           "warn_categories"
               The warning category (or categories) packed into a "SVuv".

           "flag"
               A single flag bit associated with this message, in a "SVuv".
               The bit corresponds to some bit in the *errors return value,
               such as "UTF8_GOT_LONG".

           It's important to note that specifying this parameter as non-null
           will cause any warnings this function would otherwise generate to
           be suppressed, and instead be placed in *msgs.  The caller can
           check the lexical warnings state (or not) when choosing what to do
           with the returned messages.

           If the flag "UTF8_CHECK_ONLY" is passed, no warnings are generated,
           and hence no AV is created.

           The caller, of course, is responsible for freeing any returned AV.

            UV  utf8n_to_uvchr_msgs(const U8 *s, STRLEN curlen,
                                    STRLEN *retlen, const U32 flags,
                                    U32 * errors, AV ** msgs)

       "UTF8SKIP"
           returns the number of bytes a non-malformed UTF-8 encoded character
           whose first (perhaps only) byte is pointed to by "s".

           If there is a possibility of malformed input, use instead:

           "UTF8_SAFE_SKIP" if you know the maximum ending pointer in the
           buffer pointed to by "s"; or
           "UTF8_CHK_SKIP" if you don't know it.

           It is better to restructure your code so the end pointer is passed
           down so that you know what it actually is at the point of this
           call, but if that isn't possible, "UTF8_CHK_SKIP" can minimize the
           chance of accessing beyond the end of the input buffer.

            STRLEN  UTF8SKIP(char* s)

       "UTF8_CHK_SKIP"
           This is a safer version of "UTF8SKIP", but still not as safe as
           "UTF8_SAFE_SKIP".  This version doesn't blindly assume that the
           input string pointed to by "s" is well-formed, but verifies that
           there isn't a NUL terminating character before the expected end of
           the next character in "s".  The length "UTF8_CHK_SKIP" returns
           stops just before any such NUL.

           Perl tends to add NULs, as an insurance policy, after the end of
           strings in SV's, so it is likely that using this macro will prevent
           inadvertent reading beyond the end of the input buffer, even if it
           is malformed UTF-8.

           This macro is intended to be used by XS modules where the inputs
           could be malformed, and it isn't feasible to restructure to use the
           safer "UTF8_SAFE_SKIP", for example when interfacing with a C
           library.

            STRLEN  UTF8_CHK_SKIP(char* s)

       "utf8_distance"
           Returns the number of UTF-8 characters between the UTF-8 pointers
           "a" and "b".

           WARNING: use only if you *know* that the pointers point inside the
           same UTF-8 buffer.

            IV  utf8_distance(const U8 *a, const U8 *b)

       "utf8_hop"
           Return the UTF-8 pointer "s" displaced by "off" characters, either
           forward or backward.

           WARNING: do not use the following unless you *know* "off" is within
           the UTF-8 data pointed to by "s" *and* that on entry "s" is aligned
           on the first byte of character or just after the last byte of a
           character.

            U8*  utf8_hop(const U8 *s, SSize_t off)

       "utf8_hop_back"
           Return the UTF-8 pointer "s" displaced by up to "off" characters,
           backward.

           "off" must be non-positive.

           "s" must be after or equal to "start".

           When moving backward it will not move before "start".

           Will not exceed this limit even if the string is not valid "UTF-8".

            U8*  utf8_hop_back(const U8 *s, SSize_t off, const U8 *start)

       "utf8_hop_forward"
           Return the UTF-8 pointer "s" displaced by up to "off" characters,
           forward.

           "off" must be non-negative.

           "s" must be before or equal to "end".

           When moving forward it will not move beyond "end".

           Will not exceed this limit even if the string is not valid "UTF-8".

            U8*  utf8_hop_forward(const U8 *s, SSize_t off, const U8 *end)

       "utf8_hop_safe"
           Return the UTF-8 pointer "s" displaced by up to "off" characters,
           either forward or backward.

           When moving backward it will not move before "start".

           When moving forward it will not move beyond "end".

           Will not exceed those limits even if the string is not valid
           "UTF-8".

            U8*  utf8_hop_safe(const U8 *s, SSize_t off, const U8 *start,
                               const U8 *end)

       "UTF8_IS_INVARIANT"
           Evaluates to 1 if the byte "c" represents the same character when
           encoded in UTF-8 as when not; otherwise evaluates to 0.  UTF-8
           invariant characters can be copied as-is when converting to/from
           UTF-8, saving time.

           In spite of the name, this macro gives the correct result if the
           input string from which "c" comes is not encoded in UTF-8.

           See "UVCHR_IS_INVARIANT" for checking if a UV is invariant.

            bool  UTF8_IS_INVARIANT(char c)

       "UTF8_IS_NONCHAR"
           Evaluates to non-zero if the first few bytes of the string starting
           at "s" and looking no further than "e - 1" are well-formed UTF-8
           that represents one of the Unicode non-character code points;
           otherwise it evaluates to 0.  If non-zero, the value gives how many
           bytes starting at "s" comprise the code point's representation.

            bool  UTF8_IS_NONCHAR(const U8 *s, const U8 *e)

       "UTF8_IS_SUPER"
           Recall that Perl recognizes an extension to UTF-8 that can encode
           code points larger than the ones defined by Unicode, which are
           0..0x10FFFF.

           This macro evaluates to non-zero if the first few bytes of the
           string starting at "s" and looking no further than "e - 1" are from
           this UTF-8 extension; otherwise it evaluates to 0.  If non-zero,
           the value gives how many bytes starting at "s" comprise the code
           point's representation.

           0 is returned if the bytes are not well-formed extended UTF-8, or
           if they represent a code point that cannot fit in a UV on the
           current platform.  Hence this macro can give different results when
           run on a 64-bit word machine than on one with a 32-bit word size.

           Note that it is illegal to have code points that are larger than
           what can fit in an IV on the current machine.

            bool  UTF8_IS_SUPER(const U8 *s, const U8 *e)

       "UTF8_IS_SURROGATE"
           Evaluates to non-zero if the first few bytes of the string starting
           at "s" and looking no further than "e - 1" are well-formed UTF-8
           that represents one of the Unicode surrogate code points; otherwise
           it evaluates to 0.  If non-zero, the value gives how many bytes
           starting at "s" comprise the code point's representation.

            bool  UTF8_IS_SURROGATE(const U8 *s, const U8 *e)

       "utf8_length"
           Returns the number of characters in the sequence of UTF-8-encoded
           bytes starting at "s" and ending at the byte just before "e".  If
           <s> and <e> point to the same place, it returns 0 with no warning
           raised.

           If "e < s" or if the scan would end up past "e", it raises a UTF8
           warning and returns the number of valid characters.

            STRLEN  utf8_length(const U8* s, const U8 *e)

       "UTF8_MAXBYTES"
           The maximum width of a single UTF-8 encoded character, in bytes.

           NOTE: Strictly speaking Perl's UTF-8 should not be called UTF-8
           since UTF-8 is an encoding of Unicode, and Unicode's upper limit,
           0x10FFFF, can be expressed with 4 bytes.  However, Perl thinks of
           UTF-8 as a way to encode non-negative integers in a binary format,
           even those above Unicode.

       "UTF8_MAXBYTES_CASE"
           The maximum number of UTF-8 bytes a single Unicode character can
           uppercase/lowercase/titlecase/fold into.

       "UTF8_SAFE_SKIP"
           returns 0 if "s >= e"; otherwise returns the number of bytes in the
           UTF-8 encoded character whose first  byte is pointed to by "s".
           But it never returns beyond "e".  On DEBUGGING builds, it asserts
           that "s <= e".

            STRLEN  UTF8_SAFE_SKIP(char* s, char* e)

       "UTF8_SKIP"
           This is a synonym for "UTF8SKIP"

            STRLEN  UTF8_SKIP(char* s)

       "utf8_to_bytes"
           NOTE: "utf8_to_bytes" is experimental and may change or be removed
           without notice.

           Converts a string "s" of length *lenp from UTF-8 into native byte
           encoding.  Unlike "bytes_to_utf8", this over-writes the original
           string, and updates *lenp to contain the new length.  Returns zero
           on failure (leaving "s" unchanged) setting *lenp to -1.

           Upon successful return, the number of variants in the string can be
           computed by having saved the value of *lenp before the call, and
           subtracting the after-call value of *lenp from it.

           If you need a copy of the string, see "bytes_from_utf8".

            U8*  utf8_to_bytes(U8 *s, STRLEN *lenp)

       "utf8_to_uvchr"
           "DEPRECATED!"  It is planned to remove "utf8_to_uvchr" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           Returns the native code point of the first character in the string
           "s" which is assumed to be in UTF-8 encoding; "retlen" will be set
           to the length, in bytes, of that character.

           Some, but not all, UTF-8 malformations are detected, and in fact,
           some malformed input could cause reading beyond the end of the
           input buffer, which is why this function is deprecated.  Use
           "utf8_to_uvchr_buf" instead.

           If "s" points to one of the detected malformations, and UTF8
           warnings are enabled, zero is returned and *retlen is set (if
           "retlen" isn't "NULL") to -1.  If those warnings are off, the
           computed value if well-defined (or the Unicode REPLACEMENT
           CHARACTER, if not) is silently returned, and *retlen is set (if
           "retlen" isn't NULL) so that ("s" + *retlen) is the next possible
           position in "s" that could begin a non-malformed character.  See
           "utf8n_to_uvchr" for details on when the REPLACEMENT CHARACTER is
           returned.

            UV  utf8_to_uvchr(const U8 *s, STRLEN *retlen)

       "utf8_to_uvchr_buf"
           Returns the native code point of the first character in the string
           "s" which is assumed to be in UTF-8 encoding; "send" points to 1
           beyond the end of "s".  *retlen will be set to the length, in
           bytes, of that character.

           If "s" does not point to a well-formed UTF-8 character and UTF8
           warnings are enabled, zero is returned and *retlen is set (if
           "retlen" isn't "NULL") to -1.  If those warnings are off, the
           computed value, if well-defined (or the Unicode REPLACEMENT
           CHARACTER if not), is silently returned, and *retlen is set (if
           "retlen" isn't "NULL") so that ("s" + *retlen) is the next possible
           position in "s" that could begin a non-malformed character.  See
           "utf8n_to_uvchr" for details on when the REPLACEMENT CHARACTER is
           returned.

            UV  utf8_to_uvchr_buf(const U8 *s, const U8 *send, STRLEN *retlen)

       "UVCHR_IS_INVARIANT"
           Evaluates to 1 if the representation of code point "cp" is the same
           whether or not it is encoded in UTF-8; otherwise evaluates to 0.
           UTF-8 invariant characters can be copied as-is when converting
           to/from UTF-8, saving time.  "cp" is Unicode if above 255;
           otherwise is platform-native.

            bool  UVCHR_IS_INVARIANT(UV cp)

       "UVCHR_SKIP"
           returns the number of bytes required to represent the code point
           "cp" when encoded as UTF-8.  "cp" is a native (ASCII or EBCDIC)
           code point if less than 255; a Unicode code point otherwise.

            STRLEN  UVCHR_SKIP(UV cp)

       "uvchr_to_utf8"
           Adds the UTF-8 representation of the native code point "uv" to the
           end of the string "d"; "d" should have at least "UVCHR_SKIP(uv)+1"
           (up to "UTF8_MAXBYTES+1") free bytes available.  The return value
           is the pointer to the byte after the end of the new character.  In
           other words,

               d = uvchr_to_utf8(d, uv);

           is the recommended wide native character-aware way of saying

               *(d++) = uv;

           This function accepts any code point from 0.."IV_MAX" as input.
           "IV_MAX" is typically 0x7FFF_FFFF in a 32-bit word.

           It is possible to forbid or warn on non-Unicode code points, or
           those that may be problematic by using "uvchr_to_utf8_flags".

            U8*  uvchr_to_utf8(U8 *d, UV uv)

       "uvchr_to_utf8_flags"
           Adds the UTF-8 representation of the native code point "uv" to the
           end of the string "d"; "d" should have at least "UVCHR_SKIP(uv)+1"
           (up to "UTF8_MAXBYTES+1") free bytes available.  The return value
           is the pointer to the byte after the end of the new character.  In
           other words,

               d = uvchr_to_utf8_flags(d, uv, flags);

           or, in most cases,

               d = uvchr_to_utf8_flags(d, uv, 0);

           This is the Unicode-aware way of saying

               *(d++) = uv;

           If "flags" is 0, this function accepts any code point from
           0.."IV_MAX" as input.  "IV_MAX" is typically 0x7FFF_FFFF in a
           32-bit word.

           Specifying "flags" can further restrict what is allowed and not
           warned on, as follows:

           If "uv" is a Unicode surrogate code point and
           "UNICODE_WARN_SURROGATE" is set, the function will raise a warning,
           provided UTF8 warnings are enabled.  If instead
           "UNICODE_DISALLOW_SURROGATE" is set, the function will fail and
           return NULL.  If both flags are set, the function will both warn
           and return NULL.

           Similarly, the "UNICODE_WARN_NONCHAR" and
           "UNICODE_DISALLOW_NONCHAR" flags affect how the function handles a
           Unicode non-character.

           And likewise, the "UNICODE_WARN_SUPER" and "UNICODE_DISALLOW_SUPER"
           flags affect the handling of code points that are above the Unicode
           maximum of 0x10FFFF.  Languages other than Perl may not be able to
           accept files that contain these.

           The flag "UNICODE_WARN_ILLEGAL_INTERCHANGE" selects all three of
           the above WARN flags; and "UNICODE_DISALLOW_ILLEGAL_INTERCHANGE"
           selects all three DISALLOW flags.
           "UNICODE_DISALLOW_ILLEGAL_INTERCHANGE" restricts the allowed inputs
           to the strict UTF-8 traditionally defined by Unicode.  Similarly,
           "UNICODE_WARN_ILLEGAL_C9_INTERCHANGE" and
           "UNICODE_DISALLOW_ILLEGAL_C9_INTERCHANGE" are shortcuts to select
           the above-Unicode and surrogate flags, but not the non-character
           ones, as defined in Unicode Corrigendum #9
           <https://www.unicode.org/versions/corrigendum9.html>.  See
           "Noncharacter code points" in perlunicode.

           Extremely high code points were never specified in any standard,
           and require an extension to UTF-8 to express, which Perl does.  It
           is likely that programs written in something other than Perl would
           not be able to read files that contain these; nor would Perl
           understand files written by something that uses a different
           extension.  For these reasons, there is a separate set of flags
           that can warn and/or disallow these extremely high code points,
           even if other above-Unicode ones are accepted.  They are the
           "UNICODE_WARN_PERL_EXTENDED" and "UNICODE_DISALLOW_PERL_EXTENDED"
           flags.  For more information see "UTF8_GOT_PERL_EXTENDED".  Of
           course "UNICODE_DISALLOW_SUPER" will treat all above-Unicode code
           points, including these, as malformations.  (Note that the Unicode
           standard considers anything above 0x10FFFF to be illegal, but there
           are standards predating it that allow up to 0x7FFF_FFFF (2**31 -1))

           A somewhat misleadingly named synonym for
           "UNICODE_WARN_PERL_EXTENDED" is retained for backward
           compatibility: "UNICODE_WARN_ABOVE_31_BIT".  Similarly,
           "UNICODE_DISALLOW_ABOVE_31_BIT" is usable instead of the more
           accurately named "UNICODE_DISALLOW_PERL_EXTENDED".  The names are
           misleading because on EBCDIC platforms,these flags can apply to
           code points that actually do fit in 31 bits.  The new names
           accurately describe the situation in all cases.

            U8*  uvchr_to_utf8_flags(U8 *d, UV uv, UV flags)

       "uvchr_to_utf8_flags_msgs"
           THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED
           CIRCUMSTANCES.

           Most code should use ""uvchr_to_utf8_flags"()" rather than call
           this directly.

           This function is for code that wants any warning and/or error
           messages to be returned to the caller rather than be displayed.
           All messages that would have been displayed if all lexical warnings
           are enabled will be returned.

           It is just like "uvchr_to_utf8_flags" but it takes an extra
           parameter placed after all the others, "msgs".  If this parameter
           is 0, this function behaves identically to "uvchr_to_utf8_flags".
           Otherwise, "msgs" should be a pointer to an "HV *" variable, in
           which this function creates a new HV to contain any appropriate
           messages.  The hash has three key-value pairs, as follows:

           "text"
               The text of the message as a "SVpv".

           "warn_categories"
               The warning category (or categories) packed into a "SVuv".

           "flag"
               A single flag bit associated with this message, in a "SVuv".
               The bit corresponds to some bit in the *errors return value,
               such as "UNICODE_GOT_SURROGATE".

           It's important to note that specifying this parameter as non-null
           will cause any warnings this function would otherwise generate to
           be suppressed, and instead be placed in *msgs.  The caller can
           check the lexical warnings state (or not) when choosing what to do
           with the returned messages.

           The caller, of course, is responsible for freeing any returned HV.

            U8*  uvchr_to_utf8_flags_msgs(U8 *d, UV uv, UV flags, HV ** msgs)


Utility Functions

       "C_ARRAY_END"
           Returns a pointer to one element past the final element of the
           input C array.

            void *  C_ARRAY_END(void *a)

       "C_ARRAY_LENGTH"
           Returns the number of elements in the input C array (so you want
           your zero-based indices to be less than but not equal to).

            STRLEN  C_ARRAY_LENGTH(void *a)

       "getcwd_sv"
           Fill "sv" with current working directory

            int  getcwd_sv(SV* sv)

       "IN_PERL_COMPILETIME"
           Returns 1 if this macro is being called during the compilation
           phase of the program; otherwise 0;

            bool  IN_PERL_COMPILETIME

       "IN_PERL_RUNTIME"
           Returns 1 if this macro is being called during the execution phase
           of the program; otherwise 0;

            bool  IN_PERL_RUNTIME

       "IS_SAFE_SYSCALL"
           Same as "is_safe_syscall".

            bool  IS_SAFE_SYSCALL(NN const char *pv, STRLEN len,
                                  NN const char *what, NN const char *op_name)

       "is_safe_syscall"
           Test that the given "pv" (with length "len") doesn't contain any
           internal "NUL" characters.  If it does, set "errno" to "ENOENT",
           optionally warn using the "syscalls" category, and return FALSE.

           Return TRUE if the name is safe.

           "what" and "op_name" are used in any warning.

           Used by the "IS_SAFE_SYSCALL()" macro.

            bool  is_safe_syscall(const char *pv, STRLEN len,
                                  const char *what, const char *op_name)

       "my_setenv"
           A wrapper for the C library setenv(3).  Don't use the latter, as
           the perl version has desirable safeguards

            void  my_setenv(const char* nam, const char* val)

       "Poison"
           PoisonWith(0xEF) for catching access to freed memory.

            void  Poison(void* dest, int nitems, type)

       "PoisonFree"
           PoisonWith(0xEF) for catching access to freed memory.

            void  PoisonFree(void* dest, int nitems, type)

       "PoisonNew"
           PoisonWith(0xAB) for catching access to allocated but uninitialized
           memory.

            void  PoisonNew(void* dest, int nitems, type)

       "PoisonWith"
           Fill up memory with a byte pattern (a byte repeated over and over
           again) that hopefully catches attempts to access uninitialized
           memory.

            void  PoisonWith(void* dest, int nitems, type, U8 byte)

       "StructCopy"
           This is an architecture-independent macro to copy one structure to
           another.

            void  StructCopy(type *src, type *dest, type)

       "sv_destroyable"
           Dummy routine which reports that object can be destroyed when there
           is no sharing module present.  It ignores its single SV argument,
           and returns 'true'.  Exists to avoid test for a "NULL" function
           pointer and because it could potentially warn under some level of
           strict-ness.

            bool  sv_destroyable(SV *sv)

       "sv_nosharing"
           Dummy routine which "shares" an SV when there is no sharing module
           present.  Or "locks" it.  Or "unlocks" it.  In other words, ignores
           its single SV argument.  Exists to avoid test for a "NULL" function
           pointer and because it could potentially warn under some level of
           strict-ness.

            void  sv_nosharing(SV *sv)


Versioning

       "new_version"
           Returns a new version object based on the passed in SV:

               SV *sv = new_version(SV *ver);

           Does not alter the passed in ver SV.  See "upg_version" if you want
           to upgrade the SV.

            SV*  new_version(SV *ver)

       "PERL_REVISION"
           "DEPRECATED!"  It is planned to remove "PERL_REVISION" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           The major number component of the perl interpreter currently being
           compiled or executing.  This has been 5 from 1993 into 2020.

           Instead use one of the version comparison macros.  See
           "PERL_VERSION_EQ".

       "PERL_SUBVERSION"
           "DEPRECATED!"  It is planned to remove "PERL_SUBVERSION" from a
           future release of Perl.  Do not use it for new code; remove it from
           existing code.

           The micro number component of the perl interpreter currently being
           compiled or executing.  In stable releases this gives the dot
           release number for maintenance updates.  In development releases
           this gives a tag for a snapshot of the status at various points in
           the development cycle.

           Instead use one of the version comparison macros.  See
           "PERL_VERSION_EQ".

       "PERL_VERSION"
           "DEPRECATED!"  It is planned to remove "PERL_VERSION" from a future
           release of Perl.  Do not use it for new code; remove it from
           existing code.

           The minor number component of the perl interpreter currently being
           compiled or executing.  Between 1993 into 2020, this has ranged
           from 0 to 33.

           Instead use one of the version comparison macros.  See
           "PERL_VERSION_EQ".

       "PERL_VERSION_EQ"
       "PERL_VERSION_NE"
       "PERL_VERSION_LT"
       "PERL_VERSION_LE"
       "PERL_VERSION_GT"
       "PERL_VERSION_GE"
           Returns whether or not the perl currently being compiled has the
           specified relationship to the perl given by the parameters.  For
           example,

            #if PERL_VERSION_GT(5,24,2)
              code that will only be compiled on perls after v5.24.2
            #else
              fallback code
            #endif

           Note that this is usable in making compile-time decisions

           You may use the special value '*' for the final number to mean ALL
           possible values for it.  Thus,

            #if PERL_VERSION_EQ(5,31,'*')

           means all perls in the 5.31 series.  And

            #if PERL_VERSION_NE(5,24,'*')

           means all perls EXCEPT 5.24 ones.  And

            #if PERL_VERSION_LE(5,9,'*')

           is effectively

            #if PERL_VERSION_LT(5,10,0)

           This means you don't have to think so much when converting from the
           existing deprecated "PERL_VERSION" to using this macro:

            #if PERL_VERSION <= 9

           becomes

            #if PERL_VERSION_LE(5,9,'*')

            bool  PERL_VERSION_EQ(const U8 major, const U8 minor,
                                  const U8 patch)

       "prescan_version"
           Validate that a given string can be parsed as a version object, but
           doesn't actually perform the parsing.  Can use either strict or lax
           validation rules.  Can optionally set a number of hint variables to
           save the parsing code some time when tokenizing.

            const char*  prescan_version(const char *s, bool strict,
                                         const char** errstr, bool *sqv,
                                         int *ssaw_decimal, int *swidth,
                                         bool *salpha)

       "scan_version"
           Returns a pointer to the next character after the parsed version
           string, as well as upgrading the passed in SV to an RV.

           Function must be called with an already existing SV like

               sv = newSV(0);
               s = scan_version(s, SV *sv, bool qv);

           Performs some preprocessing to the string to ensure that it has the
           correct characteristics of a version.  Flags the object if it
           contains an underscore (which denotes this is an alpha version).
           The boolean qv denotes that the version should be interpreted as if
           it had multiple decimals, even if it doesn't.

            const char*  scan_version(const char *s, SV *rv, bool qv)

       "upg_version"
           In-place upgrade of the supplied SV to a version object.

               SV *sv = upg_version(SV *sv, bool qv);

           Returns a pointer to the upgraded SV.  Set the boolean qv if you
           want to force this SV to be interpreted as an "extended" version.

            SV*  upg_version(SV *ver, bool qv)

       "vcmp"
           Version object aware cmp.  Both operands must already have been
           converted into version objects.

            int  vcmp(SV *lhv, SV *rhv)

       "vnormal"
           Accepts a version object and returns the normalized string
           representation.  Call like:

               sv = vnormal(rv);

           NOTE: you can pass either the object directly or the SV contained
           within the RV.

           The SV returned has a refcount of 1.

            SV*  vnormal(SV *vs)

       "vnumify"
           Accepts a version object and returns the normalized floating point
           representation.  Call like:

               sv = vnumify(rv);

           NOTE: you can pass either the object directly or the SV contained
           within the RV.

           The SV returned has a refcount of 1.

            SV*  vnumify(SV *vs)

       "vstringify"
           In order to maintain maximum compatibility with earlier versions of
           Perl, this function will return either the floating point notation
           or the multiple dotted notation, depending on whether the original
           version contained 1 or more dots, respectively.

           The SV returned has a refcount of 1.

            SV*  vstringify(SV *vs)

       "vverify"
           Validates that the SV contains valid internal structure for a
           version object.  It may be passed either the version object (RV) or
           the hash itself (HV).  If the structure is valid, it returns the
           HV.  If the structure is invalid, it returns NULL.

               SV *hv = vverify(sv);

           Note that it only confirms the bare minimum structure (so as not to
           get confused by derived classes which may contain additional hash
           entries):

           o   The SV is an HV or a reference to an HV

           o   The hash contains a "version" key

           o   The "version" key has a reference to an AV as its value

            SV*  vverify(SV *vs)


Warning and Dieing

       In all these calls, the "U32 wn" parameters are warning category
       constants.  You can see the ones currently available in "Category
       Hierarchy" in warnings, just capitalize all letters in the names and
       prefix them by "WARN_".  So, for example, the category "void" used in a
       perl program becomes "WARN_VOID" when used in XS code and passed to one
       of the calls below.

       "ckWARN"
       "ckWARN2"
       "ckWARN3"
       "ckWARN4"
           These return a boolean as to whether or not warnings are enabled
           for any of the warning category(ies) parameters:  "w", "w1", ....

           Should any of the categories by default be enabled even if not
           within the scope of "use warnings", instead use the "ckWARN_d"
           macros.

           The categories must be completely independent, one may not be
           subclassed from the other.

            bool  ckWARN (U32 w)
            bool  ckWARN2(U32 w1, U32 w2)
            bool  ckWARN3(U32 w1, U32 w2, U32 w3)
            bool  ckWARN4(U32 w1, U32 w2, U32 w3, U32 w4)

       "ckWARN_d"
       "ckWARN2_d"
       "ckWARN3_d"
       "ckWARN4_d"
           Like "ckWARN", but for use if and only if the warning category(ies)
           is by default enabled even if not within the scope of
           "use warnings".

            bool  ckWARN_d (U32 w)
            bool  ckWARN2_d(U32 w1, U32 w2)
            bool  ckWARN3_d(U32 w1, U32 w2, U32 w3)
            bool  ckWARN4_d(U32 w1, U32 w2, U32 w3, U32 w4)

       "ck_warner"
       "ck_warner_d"
           If none of the warning categories given by "err" are enabled, do
           nothing; otherwise call "warner"  or "warner_nocontext" with the
           passed-in parameters;.

           "err" must be one of the "packWARN", "packWARN2", "packWARN3",
           "packWARN4" macros populated with the appropriate number of warning
           categories.

           The two forms differ only in that "ck_warner_d" should be used if
           warnings for any of the categories are by default enabled.

           NOTE: "ck_warner" must be explicitly called as "Perl_ck_warner"
           with an "aTHX_" parameter.

           NOTE: "ck_warner_d" must be explicitly called as "Perl_ck_warner_d"
           with an "aTHX_" parameter.

            void  Perl_ck_warner(pTHX_ U32 err, const char* pat, ...)

       "CLEAR_ERRSV"
           Clear the contents of $@, setting it to the empty string.

           This replaces any read-only SV with a fresh SV and removes any
           magic.

            void  CLEAR_ERRSV()

       "croak"
       "croak_nocontext"
           These are XS interfaces to Perl's "die" function.

           They take a sprintf-style format pattern and argument list, which
           are used to generate a string message.  If the message does not end
           with a newline, then it will be extended with some indication of
           the current location in the code, as described for "mess_sv".

           The error message will be used as an exception, by default
           returning control to the nearest enclosing "eval", but subject to
           modification by a $SIG{__DIE__} handler.  In any case, these croak
           functions never return normally.

           For historical reasons, if "pat" is null then the contents of
           "ERRSV" ($@) will be used as an error message or object instead of
           building an error message from arguments.  If you want to throw a
           non-string object, or build an error message in an SV yourself, it
           is preferable to use the "croak_sv" function, which does not
           involve clobbering "ERRSV".

           The two forms differ only in that "croak_nocontext" does not take a
           thread context ("aTHX") parameter.  It is usually preferred as it
           takes up fewer bytes of code than plain "Perl_croak", and time is
           rarely a critical resource when you are about to throw an
           exception.

           NOTE: "croak" must be explicitly called as "Perl_croak" with an
           "aTHX_" parameter.

            void  Perl_croak     (pTHX_ const char* pat, ...)
            void  croak_nocontext(const char* pat, ...)

       "croak_no_modify"
           This encapsulates a common reason for dying, generating terser
           object code than using the generic "Perl_croak".  It is exactly
           equivalent to "Perl_croak(aTHX_ "%s", PL_no_modify)" (which expands
           to something like "Modification of a read-only value attempted").

           Less code used on exception code paths reduces CPU cache pressure.

            void  croak_no_modify()

       "croak_sv"
           This is an XS interface to Perl's "die" function.

           "baseex" is the error message or object.  If it is a reference, it
           will be used as-is.  Otherwise it is used as a string, and if it
           does not end with a newline then it will be extended with some
           indication of the current location in the code, as described for
           "mess_sv".

           The error message or object will be used as an exception, by
           default returning control to the nearest enclosing "eval", but
           subject to modification by a $SIG{__DIE__} handler.  In any case,
           the "croak_sv" function never returns normally.

           To die with a simple string message, the "croak" function may be
           more convenient.

            void  croak_sv(SV *baseex)

       "die"
           Behaves the same as "croak", except for the return type.  It should
           be used only where the "OP *" return type is required.  The
           function never actually returns.

           NOTE: "die" must be explicitly called as "Perl_die" with an "aTHX_"
           parameter.

            OP*  Perl_die(pTHX_ const char* pat, ...)

       "die_sv"
       "die_nocontext"
           These ehave the same as "croak_sv", except for the return type.  It
           should be used only where the "OP *" return type is required.  The
           functions never actually return.

           The two forms differ only in that "die_nocontext" does not take a
           thread context ("aTHX") parameter, so is used in situations where
           the caller doesn't already have the thread context.

            OP*  die_sv       (SV *baseex)
            OP*  die_nocontext(const char* pat, ...)

       "ERRSV"
           Returns the SV for $@, creating it if needed.

            SV *  ERRSV

       "packWARN"
       "packWARN2"
       "packWARN3"
       "packWARN4"
           These macros are used to pack warning categories into a single U32
           to pass to macros and functions that take a warning category
           parameter.  The number of categories to pack is given by the name,
           with a corresponding number of category parameters passed.

            U32  packWARN (U32 w1)
            U32  packWARN2(U32 w1, U32 w2)
            U32  packWARN3(U32 w1, U32 w2, U32 w3)
            U32  packWARN4(U32 w1, U32 w2, U32 w3, U32 w4)

       "PL_curcop"
           The currently active COP (control op) roughly representing the
           current statement in the source.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            COP*  PL_curcop

       "PL_curstash"
           The stash for the package code will be compiled into.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            HV*  PL_curstash

       "PL_defgv"
           The GV representing *_.  Useful for access to $_.

           On threaded perls, each thread has an independent copy of this
           variable; each initialized at creation time with the current value
           of the creating thread's copy.

            GV *  PL_defgv

       "SANE_ERRSV"
           Clean up ERRSV so we can safely set it.

           This replaces any read-only SV with a fresh writable copy and
           removes any magic.

            void  SANE_ERRSV()

       "vcroak"
           This is an XS interface to Perl's "die" function.

           "pat" and "args" are a sprintf-style format pattern and
           encapsulated argument list.  These are used to generate a string
           message.  If the message does not end with a newline, then it will
           be extended with some indication of the current location in the
           code, as described for "mess_sv".

           The error message will be used as an exception, by default
           returning control to the nearest enclosing "eval", but subject to
           modification by a $SIG{__DIE__} handler.  In any case, the "croak"
           function never returns normally.

           For historical reasons, if "pat" is null then the contents of
           "ERRSV" ($@) will be used as an error message or object instead of
           building an error message from arguments.  If you want to throw a
           non-string object, or build an error message in an SV yourself, it
           is preferable to use the "croak_sv" function, which does not
           involve clobbering "ERRSV".

            void  vcroak(const char* pat, va_list* args)

       "vwarn"
           This is an XS interface to Perl's "warn" function.

           This is like "warn", but "args" are an encapsulated argument list.

           Unlike with "vcroak", "pat" is not permitted to be null.

            void  vwarn(const char* pat, va_list* args)

       "vwarner"
           This is like "warner", but "args" are an encapsulated argument
           list.

            void  vwarner(U32 err, const char* pat, va_list* args)

       "warn"
       "warn_nocontext"
           These are XS interfaces to Perl's "warn" function.

           They take a sprintf-style format pattern and argument list, which
           are used to generate a string message.  If the message does not end
           with a newline, then it will be extended with some indication of
           the current location in the code, as described for "mess_sv".

           The error message or object will by default be written to standard
           error, but this is subject to modification by a $SIG{__WARN__}
           handler.

           Unlike with "croak", "pat" is not permitted to be null.

           The two forms differ only in that "warn_nocontext" does not take a
           thread context ("aTHX") parameter, so is used in situations where
           the caller doesn't already have the thread context.

           NOTE: "warn" must be explicitly called as "Perl_warn" with an
           "aTHX_" parameter.

            void  Perl_warn     (pTHX_ const char* pat, ...)
            void  warn_nocontext(const char* pat, ...)

       "warner"
       "warner_nocontext"
           These output a warning of the specified category (or categories)
           given by "err", using the sprintf-style format pattern "pat", and
           argument list.

           "err" must be one of the "packWARN", "packWARN2", "packWARN3",
           "packWARN4" macros populated with the appropriate number of warning
           categories.  If any of the warning categories they specify is
           fatal, a fatal exception is thrown.

           In any event a message is generated by the pattern and arguments.
           If the message does not end with a newline, then it will be
           extended with some indication of the current location in the code,
           as described for "mess_sv".

           The error message or object will by default be written to standard
           error, but this is subject to modification by a $SIG{__WARN__}
           handler.

           "pat" is not permitted to be null.

           The two forms differ only in that "warner_nocontext" does not take
           a thread context ("aTHX") parameter, so is used in situations where
           the caller doesn't already have the thread context.

           These functions differ from the similarly named "warn" functions,
           in that the latter are for XS code to unconditionally display a
           warning, whereas these are for code that may be compiling a perl
           program, and does extra checking to see if the warning should be
           fatal.

           NOTE: "warner" must be explicitly called as "Perl_warner" with an
           "aTHX_" parameter.

            void  Perl_warner     (pTHX_ U32 err, const char* pat, ...)
            void  warner_nocontext(U32 err, const char* pat, ...)

       "warn_sv"
           This is an XS interface to Perl's "warn" function.

           "baseex" is the error message or object.  If it is a reference, it
           will be used as-is.  Otherwise it is used as a string, and if it
           does not end with a newline then it will be extended with some
           indication of the current location in the code, as described for
           "mess_sv".

           The error message or object will by default be written to standard
           error, but this is subject to modification by a $SIG{__WARN__}
           handler.

           To warn with a simple string message, the "warn" function may be
           more convenient.

            void  warn_sv(SV *baseex)


XS

       xsubpp compiles XS code into C.  See "xsubpp" in perlutil.

       "ax"
           Variable which is setup by "xsubpp" to indicate the stack base
           offset, used by the "ST", "XSprePUSH" and "XSRETURN" macros.  The
           "dMARK" macro must be called prior to setup the "MARK" variable.

            I32  ax

       "CLASS"
           Variable which is setup by "xsubpp" to indicate the class name for
           a C++ XS constructor.  This is always a "char*".  See "THIS".

            char*  CLASS

       "dAX"
           Sets up the "ax" variable.  This is usually handled automatically
           by "xsubpp" by calling "dXSARGS".

              dAX;

       "dAXMARK"
           Sets up the "ax" variable and stack marker variable "mark".  This
           is usually handled automatically by "xsubpp" by calling "dXSARGS".

              dAXMARK;

       "dITEMS"
           Sets up the "items" variable.  This is usually handled
           automatically by "xsubpp" by calling "dXSARGS".

              dITEMS;

       "dMY_CXT_SV"
           Now a placeholder that declares nothing

              dMY_CXT_SV;

       "dUNDERBAR"
           Sets up any variable needed by the "UNDERBAR" macro.  It used to
           define "padoff_du", but it is currently a noop.  However, it is
           strongly advised to still use it for ensuring past and future
           compatibility.

              dUNDERBAR;

       "dXSARGS"
           Sets up stack and mark pointers for an XSUB, calling "dSP" and
           "dMARK".  Sets up the "ax" and "items" variables by calling "dAX"
           and "dITEMS".  This is usually handled automatically by "xsubpp".

              dXSARGS;

       "dXSI32"
           Sets up the "ix" variable for an XSUB which has aliases.  This is
           usually handled automatically by "xsubpp".

              dXSI32;

       "items"
           Variable which is setup by "xsubpp" to indicate the number of items
           on the stack.  See "Variable-length Parameter Lists" in perlxs.

            I32  items

       "ix"
           Variable which is setup by "xsubpp" to indicate which of an XSUB's
           aliases was used to invoke it.  See "The ALIAS: Keyword" in perlxs.

            I32  ix

       "RETVAL"
           Variable which is setup by "xsubpp" to hold the return value for an
           XSUB.  This is always the proper type for the XSUB.  See "The
           RETVAL Variable" in perlxs.

            type  RETVAL

       "ST"
           Used to access elements on the XSUB's stack.

            SV*  ST(int ix)

       "THIS"
           Variable which is setup by "xsubpp" to designate the object in a
           C++ XSUB.  This is always the proper type for the C++ object.  See
           "CLASS" and "Using XS With C++" in perlxs.

            type  THIS

       "UNDERBAR"
           The SV* corresponding to the $_ variable.  Works even if there is a
           lexical $_ in scope.

       "XS"
           Macro to declare an XSUB and its C parameter list.  This is handled
           by "xsubpp".  It is the same as using the more explicit
           "XS_EXTERNAL" macro; the latter is preferred.

       "XS_EXTERNAL"
           Macro to declare an XSUB and its C parameter list explicitly
           exporting the symbols.

       "XS_INTERNAL"
           Macro to declare an XSUB and its C parameter list without exporting
           the symbols.  This is handled by "xsubpp" and generally preferable
           over exporting the XSUB symbols unnecessarily.

       "XSPROTO"
           Macro used by "XS_INTERNAL" and "XS_EXTERNAL" to declare a function
           prototype.  You probably shouldn't be using this directly yourself.


Undocumented elements

       The following functions have been flagged as part of the public API,
       but are currently undocumented.  Use them at your own risk, as the
       interfaces are subject to change.  Functions that are not listed in
       this document are not intended for public use, and should NOT be used
       under any circumstances.

       If you feel you need to use one of these functions, first send email to
       perl5-porters@perl.org <mailto:perl5-porters@perl.org>.  It may be that
       there is a good reason for the function not being documented, and it
       should be removed from this list; or it may just be that no one has
       gotten around to documenting it.  In the latter case, you will be asked
       to submit a patch to document the function.  Once your patch is
       accepted, it will indicate that the interface is stable (unless it is
       explicitly marked otherwise) and usable by you.



        amagic_call        gv_name_set            PerlIO_fill
        amagic_deref_call  gv_SVadd               PerlIO_unread
        any_dup            he_dup                 pmop_dump
        atfork_lock        hek_dup                pop_scope
        atfork_unlock      hv_delayfree_ent       pregfree
        block_gimme        hv_eiter_p             ptr_table_fetch
        call_atexit        hv_eiter_set           ptr_table_free
        call_list          hv_free_ent            ptr_table_new
        clear_defarray     hv_ksplit              ptr_table_split
        clone_params_del   hv_name_set            ptr_table_store
        clone_params_new   hv_placeholders_get    push_scope
        CvDEPTH            hv_placeholders_set    re_compile
        deb                hv_rand_set            regdump
        deb_nocontext      hv_riter_p             repeatcpy
        debop              hv_riter_set           rsignal_state
        debprofdump        init_stacks            rvpv_dup
        debstack           init_tm                save_adelete
        debstackptrs       is_lvalue_sub          save_aelem
        dirp_dup           leave_scope            save_aelem_flags
        do_aspawn          magic_dump             save_alloc
        do_close           markstack_grow         save_generic_pvref
        do_join            mfree                  save_generic_svref
        do_open            mg_dup                 save_hdelete
        do_openn           mg_size                save_helem
        doref              mro_get_from_name      save_helem_flags
        do_spawn           mro_set_mro            save_hints
        do_spawn_nowait    my_chsize              save_op
        do_sprintf         my_cxt_init            save_padsv_and_mortalize
        dounwind           my_dirfd               save_pushi32ptr
        dowantarray        my_failure_exit        save_pushptr
        dump_eval          my_fflush_all          save_pushptrptr
        dump_form          my_fork                save_set_svflags
        dump_mstats        my_pclose              save_shared_pvref
        dump_sub           my_popen               savestack_grow
        filter_del         my_popen_list          savestack_grow_cnt
        fp_dup             my_socketpair          save_vptr
        get_context        newANONATTRSUB         scan_vstring
        get_mstats         newANONHASH            seed
        get_op_descs       newANONLIST            set_context
        get_op_names       newANONSUB             share_hek
        get_ppaddr         newAVREF               si_dup
        get_vtbl           newCVREF               ss_dup
        gp_dup             newFORM                start_subparse
        gp_free            newGVgen               sv_2pvbyte_flags
        gp_ref             newGVgen_flags         sv_2pvutf8_flags
        gv_add_by_type     newGVREF               SvAMAGIC_off
        Gv_AMupdate        newHVhv                SvAMAGIC_on
        gv_autoload_pv     newHVREF               sv_dup
        gv_autoload_pvn    newIO                  sv_dup_inc
        gv_autoload_sv     newMYSUB               sv_peek
        gv_AVadd           newPROG                sys_intern_clear
        gv_dump            new_stackinfo          sys_intern_dup
        gv_efullname3      newSVREF               sys_intern_init
        gv_efullname4      op_refcnt_lock         taint_env
        gv_fullname3       op_refcnt_unlock       taint_proper
        gv_fullname4       parser_dup             unsharepvn
        gv_handler         perl_alloc_using       vdeb
        gv_HVadd           perl_clone_using
        gv_IOadd           PerlIO_context_layers


AUTHORS

       Until May 1997, this document was maintained by Jeff Okamoto
       <okamoto@corp.hp.com>.  It is now maintained as part of Perl itself.

       With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
       Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
       Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
       Stephen McCamant, and Gurusamy Sarathy.

       API Listing originally by Dean Roehrich <roehrich@cray.com>.

       Updated to be autogenerated from comments in the source by Benjamin
       Stuhl.


SEE ALSO

       config.h, perlapio(1), perlcall(1), perlclib(1), perlfilter(1),
       perlguts(1), perlintern(1), perlinterp(1), perliol(1), perlmroapi(1),
       perlreguts(1), perlxs(1)



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