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PERL5300DELTA(1pm)     Perl Programmers Reference Guide     PERL5300DELTA(1pm)




NAME

       perl5300delta - what is new for perl v5.30.0


DESCRIPTION

       This document describes differences between the 5.28.0 release and the
       5.30.0 release.

       If you are upgrading from an earlier release such as 5.26.0, first read
       perl5280delta, which describes differences between 5.26.0 and 5.28.0.


Notice

       sv_utf8_(downgrade|decode) are no longer marked as experimental.  [GH
       #16822] <https://github.com/Perl/perl5/issues/16822>.


Core Enhancements

   Limited variable length lookbehind in regular expression pattern matching
       is now experimentally supported
       Using a lookbehind assertion (like "(?<=foo?)" or "(?<!ba{1,9}r)"
       previously would generate an error and refuse to compile.  Now it
       compiles (if the maximum lookbehind is at most 255 characters), but
       raises a warning in the new "experimental::vlb" warnings category.
       This is to caution you that the precise behavior is subject to change
       based on feedback from use in the field.

       See "(?<=pattern)" in perlre and "(?<!pattern)" in perlre.

   The upper limit "n" specifiable in a regular expression quantifier of the
       form "{m,n}" has been doubled to 65534
       The meaning of an unbounded upper quantifier "{m,}" remains unchanged.
       It matches 2**31 - 1 times on most platforms, and more on ones where a
       C language short variable is more than 4 bytes long.

   Unicode 12.1 is supported
       Because of a change in Unicode release cycles, Perl jumps from Unicode
       10.0 in Perl 5.28 to Unicode 12.1 in Perl 5.30.

       For details on the Unicode changes, see
       <https://www.unicode.org/versions/Unicode11.0.0/> for 11.0;
       <https://www.unicode.org/versions/Unicode12.0.0/> for 12.0; and
       <https://www.unicode.org/versions/Unicode12.1.0/> for 12.1.  (Unicode
       12.1 differs from 12.0 only in the addition of a single character, that
       for the new Japanese era name.)

       The Word_Break property, as in past Perl releases, remains tailored to
       behave more in line with expectations of Perl users.  This means that
       sequential runs of horizontal white space characters are not broken
       apart, but kept as a single run.  Unicode 11 changed from past versions
       to be more in line with Perl, but it left several white space
       characters as causing breaks: TAB, NO BREAK SPACE, and FIGURE SPACE
       (U+2007).  We have decided to continue to use the previous Perl
       tailoring with regards to these.

   Wildcards in Unicode property value specifications are now partially
       supported
       You can now do something like this in a regular expression pattern

        qr! \p{nv= /(?x) \A [0-5] \z / }!

       which matches all Unicode code points whose numeric value is between 0
       and 5 inclusive.  So, it could match the Thai or Bengali digits whose
       numeric values are 0, 1, 2, 3, 4, or 5.

       This marks another step in implementing the regular expression features
       the Unicode Consortium suggests.

       Most properties are supported, with the remainder planned for 5.32.
       Details are in "Wildcards in Property Values" in perlunicode.

   qr'\N{name}' is now supported
       Previously it was an error to evaluate a named character "\N{...}"
       within a single quoted regular expression pattern (whose evaluation is
       deferred from the normal place).  This restriction is now removed.

   Turkic UTF-8 locales are now seamlessly supported
       Turkic languages have different casing rules than other languages for
       the characters "i" and "I".  The uppercase of "i" is LATIN CAPITAL
       LETTER I WITH DOT ABOVE (U+0130); and the lowercase of "I" is LATIN
       SMALL LETTER DOTLESS I (U+0131).  Unicode furnishes alternate casing
       rules for use with Turkic languages.  Previously, Perl ignored these,
       but now, it uses them when it detects that it is operating under a
       Turkic UTF-8 locale.

   It is now possible to compile perl to always use thread-safe locale
       operations.
       Previously, these calls were only used when the perl was compiled to be
       multi-threaded.  To always enable them, add

        -Accflags='-DUSE_THREAD_SAFE_LOCALE'

       to your Configure flags.

   Eliminate opASSIGN macro usage from core
       This macro is still defined but no longer used in core

   "-Drv" now means something on "-DDEBUGGING" builds
       Now, adding the verbose flag ("-Dv") to the "-Dr" flag turns on all
       possible regular expression debugging.


Incompatible Changes

   Assigning non-zero to $[ is fatal
       Setting $[ to a non-zero value has been deprecated since Perl 5.12 and
       now throws a fatal error.  See "Assigning non-zero to $[ is fatal" in
       perldeprecation.

   Delimiters must now be graphemes
       See "Use of unassigned code point or non-standalone grapheme for a
       delimiter." in perldeprecation

   Some formerly deprecated uses of an unescaped left brace "{" in regular
       expression patterns are now illegal
       But to avoid breaking code unnecessarily, most instances that issued a
       deprecation warning, remain legal and now have a non-deprecation
       warning raised.  See "Unescaped left braces in regular expressions" in
       perldeprecation.

   Previously deprecated sysread()/syswrite() on :utf8 handles is now fatal
       Calling sysread(), syswrite(), send() or recv() on a ":utf8" handle,
       whether applied explicitly or implicitly, is now fatal.  This was
       deprecated in perl 5.24.

       There were two problems with calling these functions on ":utf8"
       handles:

       o   All four functions only paid attention to the ":utf8" flag.  Other
           layers were completely ignored, so a handle with
           ":encoding(UTF-16LE)" layer would be treated as UTF-8.  Other
           layers, such as compression are completely ignored with or without
           the ":utf8" flag.

       o   sysread() and recv() would read from the handle, skipping any
           validation by the layers, and do no validation of their own.  This
           could lead to invalidly encoded perl scalars.

       [GH #14839] <https://github.com/Perl/perl5/issues/14839>.

   my() in false conditional prohibited
       Declarations such as "my $x if 0" are no longer permitted.

       [GH #16702] <https://github.com/Perl/perl5/issues/16702>.

   Fatalize $* and $#
       These special variables, long deprecated, now throw exceptions when
       used.

       [GH #16718] <https://github.com/Perl/perl5/issues/16718>.

   Fatalize unqualified use of dump()
       The "dump()" function, long discouraged, may no longer be used unless
       it is fully qualified, i.e., "CORE::dump()".

       [GH #16719] <https://github.com/Perl/perl5/issues/16719>.

   Remove File::Glob::glob()
       The "File::Glob::glob()" function, long deprecated, has been removed
       and now throws an exception which advises use of
       "File::Glob::bsd_glob()" instead.

       [GH #16721] <https://github.com/Perl/perl5/issues/16721>.

   "pack()" no longer can return malformed UTF-8
       It croaks if it would otherwise return a UTF-8 string that contains
       malformed UTF-8.  This protects against potential security threats.
       This is considered a bug fix as well.  [GH #16035]
       <https://github.com/Perl/perl5/issues/16035>.

   Any set of digits in the Common script are legal in a script run of another
       script
       There are several sets of digits in the Common script.  "[0-9]" is the
       most familiar.  But there are also "[\x{FF10}-\x{FF19}]" (FULLWIDTH
       DIGIT ZERO - FULLWIDTH DIGIT NINE), and several sets for use in
       mathematical notation, such as the MATHEMATICAL DOUBLE-STRUCK DIGITs.
       Any of these sets should be able to appear in script runs of, say,
       Greek.  But the design of 5.30 overlooked all but the ASCII digits
       "[0-9]", so the design was flawed.  This has been fixed, so is both a
       bug fix and an incompatibility.  [GH #16704]
       <https://github.com/Perl/perl5/issues/16704>.

       All digits in a run still have to come from the same set of ten digits.

   JSON::PP enables allow_nonref by default
       As JSON::XS 4.0 changed its policy and enabled allow_nonref by default,
       JSON::PP also enabled allow_nonref by default.


Deprecations

   In XS code, use of various macros dealing with UTF-8.
       This deprecation was scheduled to become fatal in 5.30, but has been
       delayed to 5.32 due to problems that showed up with some CPAN modules.
       For details of what's affected, see perldeprecation.


Performance Enhancements

       o   Translating from UTF-8 into the code point it represents now is
           done via a deterministic finite automaton, speeding it up.  As a
           typical example, "ord("\x7fff")" now requires 12% fewer
           instructions than before.  The performance of checking that a
           sequence of bytes is valid UTF-8 is similarly improved, again by
           using a DFA.

       o   Eliminate recursion from finalize_op().  [GH #11866]
           <https://github.com/Perl/perl5/issues/11866>.

       o   A handful of small optimizations related to character folding and
           character classes in regular expressions.

       o   Optimization of "IV" to "UV" conversions.  [GH #16761]
           <https://github.com/Perl/perl5/issues/16761>.

       o   Speed up of the integer stringification algorithm by processing two
           digits at a time instead of one.  [GH #16769]
           <https://github.com/Perl/perl5/issues/16769>.

       o   Improvements based on LGTM analysis and recommendation.
           (<https://lgtm.com/projects/g/Perl/perl5/alerts/?mode=tree>).  [GH
           #16765] <https://github.com/Perl/perl5/issues/16765>.  [GH #16773]
           <https://github.com/Perl/perl5/issues/16773>.

       o   Code optimizations in regcomp.c, regcomp.h, regexec.c.

       o   Regular expression pattern matching of things like "qr/[^a]/" is
           significantly sped up, where a is any ASCII character.  Other
           classes can get this speed up, but which ones is complicated and
           depends on the underlying bit patterns of those characters, so
           differs between ASCII and EBCDIC platforms, but all case pairs,
           like "qr/[Gg]/" are included, as is "[^01]".


Modules and Pragmata

   Updated Modules and Pragmata
       o   Archive::Tar has been upgraded from version 2.30 to 2.32.

       o   B has been upgraded from version 1.74 to 1.76.

       o   B::Concise has been upgraded from version 1.003 to 1.004.

       o   B::Deparse has been upgraded from version 1.48 to 1.49.

       o   bignum has been upgraded from version 0.49 to 0.51.

       o   bytes has been upgraded from version 1.06 to 1.07.

       o   Carp has been upgraded from version 1.38 to 1.50

       o   Compress::Raw::Bzip2 has been upgraded from version 2.074 to 2.084.

       o   Compress::Raw::Zlib has been upgraded from version 2.076 to 2.084.

       o   Config::Extensions has been upgraded from version 0.02 to 0.03.

       o   Config::Perl::V. has been upgraded from version 0.29 to 0.32. This
           was due to a new configuration variable that has influence on
           binary compatibility: "USE_THREAD_SAFE_LOCALE".

       o   CPAN has been upgraded from version 2.20 to 2.22.

       o   Data::Dumper has been upgraded from version 2.170 to 2.174

           Data::Dumper now avoids leaking when "croak"ing.

       o   DB_File has been upgraded from version 1.840 to 1.843.

       o   deprecate has been upgraded from version 0.03 to 0.04.

       o   Devel::Peek has been upgraded from version 1.27 to 1.28.

       o   Devel::PPPort has been upgraded from version 3.40 to 3.52.

       o   Digest::SHA has been upgraded from version 6.01 to 6.02.

       o   Encode has been upgraded from version 2.97 to 3.01.

       o   Errno has been upgraded from version 1.29 to 1.30.

       o   experimental has been upgraded from version 0.019 to 0.020.

       o   ExtUtils::CBuilder has been upgraded from version 0.280230 to
           0.280231.

       o   ExtUtils::Manifest has been upgraded from version 1.70 to 1.72.

       o   ExtUtils::Miniperl has been upgraded from version 1.08 to 1.09.

       o   ExtUtils::ParseXS has been upgraded from version 3.39 to 3.40.
           "OUTLIST" parameters are no longer incorrectly included in the
           automatically generated function prototype.  [GH #16746]
           <https://github.com/Perl/perl5/issues/16746>.

       o   feature has been upgraded from version 1.52 to 1.54.

       o   File::Copy has been upgraded from version 2.33 to 2.34.

       o   File::Find has been upgraded from version 1.34 to 1.36.

           $File::Find::dont_use_nlink now defaults to 1 on all platforms.
           [GH #16759] <https://github.com/Perl/perl5/issues/16759>.

           Variables $Is_Win32 and $Is_VMS are being initialized.

       o   File::Glob has been upgraded from version 1.31 to 1.32.

       o   File::Path has been upgraded from version 2.15 to 2.16.

       o   File::Spec has been upgraded from version 3.74 to 3.78.

           Silence Cwd warning on Android builds if "targetsh" is not defined.

       o   File::Temp has been upgraded from version 0.2304 to 0.2309.

       o   Filter::Util::Call has been upgraded from version 1.58 to 1.59.

       o   GDBM_File has been upgraded from version 1.17 to 1.18.

       o   HTTP::Tiny has been upgraded from version 0.070 to 0.076.

       o   I18N::Langinfo has been upgraded from version 0.17 to 0.18.

       o   IO has been upgraded from version 1.39 to 1.40.

       o   IO-Compress has been upgraded from version 2.074 to 2.084.

           Adds support for "IO::Uncompress::Zstd" and
           "IO::Uncompress::UnLzip".

           The "BinModeIn" and "BinModeOut" options are now no-ops.  ALL files
           will be read/written in binmode.

       o   IPC::Cmd has been upgraded from version 1.00 to 1.02.

       o   JSON::PP has been upgraded from version 2.97001 to 4.02.

           JSON::PP as JSON::XS 4.0 enables "allow_nonref" by default.

       o   lib has been upgraded from version 0.64 to 0.65.

       o   Locale::Codes has been upgraded from version 3.56 to 3.57.

       o   Math::BigInt has been upgraded from version 1.999811 to 1.999816.

           "bnok()" now supports the full Kronenburg extension.  [cpan #95628]
           <https://rt.cpan.org/Ticket/Display.html?id=95628>.

       o   Math::BigInt::FastCalc has been upgraded from version 0.5006 to
           0.5008.

       o   Math::BigRat has been upgraded from version 0.2613 to 0.2614.

       o   Module::CoreList has been upgraded from version 5.20180622 to
           5.20190520.

           Changes to B::Op_private and Config

       o   Module::Load has been upgraded from version 0.32 to 0.34.

       o   Module::Metadata has been upgraded from version 1.000033 to
           1.000036.

           Properly clean up temporary directories after testing.

       o   NDBM_File has been upgraded from version 1.14 to 1.15.

       o   Net::Ping has been upgraded from version 2.62 to 2.71.

       o   ODBM_File has been upgraded from version 1.15 to 1.16.

       o   PathTools has been upgraded from version 3.74 to 3.78.

       o   parent has been upgraded from version 0.236 to 0.237.

       o   perl5db.pl has been upgraded from version 1.54 to 1.55.

           Debugging threaded code no longer deadlocks in "DB::sub" nor
           "DB::lsub".

       o   perlfaq has been upgraded from version 5.021011 to 5.20190126.

       o   PerlIO::encoding has been upgraded from version 0.26 to 0.27.

           Warnings enabled by setting the "WARN_ON_ERR" flag in
           $PerlIO::encoding::fallback are now only produced if warnings are
           enabled with "use warnings "utf8";" or setting $^W.

       o   PerlIO::scalar has been upgraded from version 0.29 to 0.30.

       o   podlators has been upgraded from version 4.10 to 4.11.

       o   POSIX has been upgraded from version 1.84 to 1.88.

       o   re has been upgraded from version 0.36 to 0.37.

       o   SDBM_File has been upgraded from version 1.14 to 1.15.

       o   sigtrap has been upgraded from version 1.08 to 1.09.

       o   Storable has been upgraded from version 3.08 to 3.15.

           Storable no longer probes for recursion limits at build time.  [GH
           #16780] <https://github.com/Perl/perl5/issues/16780> and others.

           Metasploit exploit code was included to test for CVE-2015-1992
           detection, this caused anti-virus detections on at least one AV
           suite.  The exploit code has been removed and replaced with a
           simple functional test.  [GH #16778]
           <https://github.com/Perl/perl5/issues/16778>

       o   Test::Simple has been upgraded from version 1.302133 to 1.302162.

       o   Thread::Queue has been upgraded from version 3.12 to 3.13.

       o   threads::shared has been upgraded from version 1.58 to 1.60.

           Added support for extra tracing of locking, this requires a
           "-DDEBUGGING" and extra compilation flags.

       o   Time::HiRes has been upgraded from version 1.9759 to 1.9760.

       o   Time::Local has been upgraded from version 1.25 to 1.28.

       o   Time::Piece has been upgraded from version 1.3204 to 1.33.

       o   Unicode::Collate has been upgraded from version 1.25 to 1.27.

       o   Unicode::UCD has been upgraded from version 0.70 to 0.72.

       o   User::grent has been upgraded from version 1.02 to 1.03.

       o   utf8 has been upgraded from version 1.21 to 1.22.

       o   vars has been upgraded from version 1.04 to 1.05.

           "vars.pm" no longer disables non-vars strict when checking if
           strict vars is enabled.  [GH #15851]
           <https://github.com/Perl/perl5/issues/15851>.

       o   version has been upgraded from version 0.9923 to 0.9924.

       o   warnings has been upgraded from version 1.42 to 1.44.

       o   XS::APItest has been upgraded from version 0.98 to 1.00.

       o   XS::Typemap has been upgraded from version 0.16 to 0.17.

   Removed Modules and Pragmata
       The following modules will be removed from the core distribution in a
       future release, and will at that time need to be installed from CPAN.
       Distributions on CPAN which require these modules will need to list
       them as prerequisites.

       The core versions of these modules will now issue "deprecated"-category
       warnings to alert you to this fact.  To silence these deprecation
       warnings, install the modules in question from CPAN.

       Note that these are (with rare exceptions) fine modules that you are
       encouraged to continue to use.  Their disinclusion from core primarily
       hinges on their necessity to bootstrapping a fully functional, CPAN-
       capable Perl installation, not usually on concerns over their design.

       o   B::Debug is no longer distributed with the core distribution.  It
           continues to be available on CPAN as "B::Debug
           <https://metacpan.org/pod/B::Debug>".

       o   Locale::Codes has been removed at the request of its author.  It
           continues to be available on CPAN as "Locale::Codes
           <https://metacpan.org/pod/Locale::Codes>" [GH #16660]
           <https://github.com/Perl/perl5/issues/16660>.


Documentation

   Changes to Existing Documentation
       We have attempted to update the documentation to reflect the changes
       listed in this document.  If you find any we have missed, send email to
       perlbug@perl.org <mailto:perlbug@perl.org>.

       perlapi

       o   "AvFILL()" was wrongly listed as deprecated.  This has been
           corrected.  [GH #16586]
           <https://github.com/Perl/perl5/issues/16586>

       perlop

       o   We no longer have null (empty line) here doc terminators, so perlop
           should not refer to them.

       o   The behaviour of "tr" when the delimiter is an apostrophe has been
           clarified.  In particular, hyphens aren't special, and "\x{}" isn't
           interpolated.  [GH #15853]
           <https://github.com/Perl/perl5/issues/15853>

       perlreapi, perlvar

       o   Improve docs for lastparen, lastcloseparen.

       perlfunc

       o   The entry for "-X" in perlfunc has been clarified to indicate that
           symbolic links are followed for most tests.

       o   Clarification of behaviour of "reset EXPR".

       o   Try to clarify that "ref(qr/xx/)" returns "Regexp" rather than
           "REGEXP" and why.  [GH #16801]
           <https://github.com/Perl/perl5/issues/16801>.

       perlreref

       o   Clarification of the syntax of /(?(cond)yes)/.

       perllocale

       o   There are actually two slightly different types of UTF-8 locales:
           one for Turkic languages and one for everything else. Starting in
           Perl v5.30, Perl seamlessly handles both types.

       perlrecharclass

       o   Added a note for the ::xdigit:: character class.

       perlvar

       o   More specific documentation of paragraph mode.  [GH #16787]
           <https://github.com/Perl/perl5/issues/16787>.


Diagnostics

       The following additions or changes have been made to diagnostic output,
       including warnings and fatal error messages.  For the complete list of
       diagnostic messages, see perldiag.

   Changes to Existing Diagnostics
       o   As noted under "Incompatible Changes" above, the deprecation
           warning "Unescaped left brace in regex is deprecated here (and will
           be fatal in Perl 5.30), passed through in regex; marked by <-- HERE
           in m/%s/" has been changed to the non-deprecation warning
           "Unescaped left brace in regex is passed through in regex; marked
           by <-- HERE in m/%s/".

       o   Specifying "\o{}" without anything between the braces now yields
           the fatal error message "Empty \o{}".  Previously it was  "Number
           with no digits".  This means the same wording is used for this kind
           of error as with similar constructs such as "\p{}".

       o   Within the scope of the experimental feature "use re 'strict'",
           specifying "\x{}" without anything between the braces now yields
           the fatal error message "Empty \x{}".  Previously it was  "Number
           with no digits".  This means the same wording is used for this kind
           of error as with similar constructs such as "\p{}".  It is legal,
           though not wise to have an empty "\x" outside of "re 'strict'"; it
           silently generates a NUL character.

       o   Type of arg %d to %s must be %s (not %s)

           Attempts to push, pop, etc on a hash or glob now produce this
           message rather than complaining that they no longer work on
           scalars.  [GH #15774] <https://github.com/Perl/perl5/issues/15774>.

       o   Prototype not terminated

           The file and line number is now reported for this error.  [GH
           #16697] <https://github.com/Perl/perl5/issues/16697>

       o   Under "-Dr" (or "use re 'Debug'") the compiled regex engine program
           is displayed. It used to use two different spellings for infinity,
           "INFINITY", and "INFTY". It now uses the latter exclusively, as
           that spelling has been around the longest.


Utility Changes

   xsubpp
       o   The generated prototype (with "PROTOTYPES: ENABLE") would include
           "OUTLIST" parameters, but these aren't arguments to the perl
           function.  This has been rectified.  [GH #16746]
           <https://github.com/Perl/perl5/issues/16746>.


Configuration and Compilation

       o   Normally the thread-safe locale functions are used only on threaded
           builds.  It is now possible to force their use on unthreaded builds
           on systems that have them available, by including the
           "-Accflags='-DUSE_THREAD_SAFE_LOCALE'" option to Configure.

       o   Improve detection of memrchr, strlcat, and strlcpy

       o   Improve Configure detection of memmem().  [GH #16807]
           <https://github.com/Perl/perl5/issues/16807>.

       o   Multiple improvements and fixes for -DPERL_GLOBAL_STRUCT build
           option.

       o   Fix -DPERL_GLOBAL_STRUCT_PRIVATE build option.


Testing

       o   t/lib/croak/op [GH #15774]
           <https://github.com/Perl/perl5/issues/15774>.

           separate error for "push", etc. on hash/glob.

       o   t/op/svleak.t [GH #16749]
           <https://github.com/Perl/perl5/issues/16749>.

           Add test for "goto &sub" in overload leaking.

       o   Split t/re/fold_grind.t into multiple test files.

       o   Fix intermittent tests which failed due to race conditions which
           surface during parallel testing.  [GH #16795]
           <https://github.com/Perl/perl5/issues/16795>.

       o   Thoroughly test paragraph mode, using a new test file,
           t/io/paragraph_mode.t.  [GH #16787]
           <https://github.com/Perl/perl5/issues/16787>.

       o   Some tests in t/io/eintr.t caused the process to hang on pre-16
           Darwin. These tests are skipped for those version of Darwin.


Platform Support

   Platform-Specific Notes
       HP-UX 11.11
           An obscure problem in "pack()" when compiling with HP C-ANSI-C has
           been fixed by disabling optimizations in pp_pack.c.

       Mac OS X
           Perl's build and testing process on Mac OS X for "-Duseshrplib"
           builds is now compatible with Mac OS X System Integrity Protection
           (SIP).

           SIP prevents binaries in /bin (and a few other places) being passed
           the "DYLD_LIBRARY_PATH" environment variable.  For our purposes
           this prevents "DYLD_LIBRARY_PATH" from being passed to the shell,
           which prevents that variable being passed to the testing or build
           process, so running "perl" couldn't find libperl.dylib.

           To work around that, the initial build of the perl executable
           expects to find libperl.dylib in the build directory, and the
           library path is then adjusted during installation to point to the
           installed library.

           [GH #15057] <https://github.com/Perl/perl5/issues/15057>.

       Minix3
           Some support for Minix3 has been re-added.

       Cygwin
           Cygwin doesn't make "cuserid" visible.

       Win32 Mingw
           C99 math functions are now available.

       Windows
           o   The "USE_CPLUSPLUS" build option which has long been available
               in win32/Makefile (for nmake) and win32/makefile.mk (for dmake)
               is now also available in win32/GNUmakefile (for gmake).

           o   The nmake makefile no longer defaults to Visual C++ 6.0 (a very
               old version which is unlikely to be widely used today).  As a
               result, it is now a requirement to specify the "CCTYPE" since
               there is no obvious choice of which modern version to default
               to instead.  Failure to specify "CCTYPE" will result in an
               error being output and the build will stop.

               (The dmake and gmake makefiles will automatically detect which
               compiler is being used, so do not require "CCTYPE" to be set.
               This feature has not yet been added to the nmake makefile.)

           o   "sleep()" with warnings enabled for a "USE_IMP_SYS" build no
               longer warns about the sleep timeout being too large.  [GH
               #16631] <https://github.com/Perl/perl5/issues/16631>.

           o   Support for compiling perl on Windows using Microsoft Visual
               Studio 2019 (containing Visual C++ 14.2) has been added.

           o   socket() now sets $! if the protocol, address family and socket
               type combination is not found.  [GH #16849]
               <https://github.com/Perl/perl5/issues/16849>.

           o   The Windows Server 2003 SP1 Platform SDK build, with its early
               x64 compiler and tools, was accidentally broken in Perl 5.27.9.
               This has now been fixed.


Internal Changes

       o   The sizing pass has been eliminated from the regular expression
           compiler.  An extra pass may instead be needed in some cases to
           count the number of parenthetical capture groups.

       o   A new function ""my_strtod"" in perlapi or its synonym, Strtod(),
           is now available with the same signature as the libc strtod().  It
           provides strotod() equivalent behavior on all platforms, using the
           best available precision, depending on platform capabilities and
           Configure options, while handling locale-related issues, such as if
           the radix character should be a dot or comma.

       o   Added "newSVsv_nomg()" to copy a SV without processing get magic on
           the source.  [GH #16461]
           <https://github.com/Perl/perl5/issues/16461>.

       o   It is now forbidden to malloc more than "PTRDIFF_T_MAX" bytes.
           Much code (including C optimizers) assumes that all data structures
           will not be larger than this, so this catches such attempts before
           overflow happens.

       o   Two new regnodes have been introduced "EXACT_ONLY8", and
           "EXACTFU_ONLY8". They're equivalent to "EXACT" and "EXACTFU",
           except that they contain a code point which requires UTF-8 to
           represent/match. Hence, if the target string isn't UTF-8, we know
           it can't possibly match, without needing to try.

       o   "print_bytes_for_locale()" is now defined if "DEBUGGING", Prior, it
           didn't get defined unless "LC_COLLATE" was defined on the platform.


Selected Bug Fixes

       o   Compilation under "-DPERL_MEM_LOG" and "-DNO_LOCALE" have been
           fixed.

       o   Perl 5.28 introduced an "index()" optimization when comparing to -1
           (or indirectly, e.g. >= 0).  When this optimization was triggered
           inside a "when" clause it caused a warning ("Argument %s isn't
           numeric in smart match").  This has now been fixed.  [GH #16626]
           <https://github.com/Perl/perl5/issues/16626>

       o   The new in-place editing code no longer leaks directory handles.
           [GH #16602] <https://github.com/Perl/perl5/issues/16602>.

       o   Warnings produced from constant folding operations on overloaded
           values no longer produce spurious "Use of uninitialized value"
           warnings.  [GH #16349]
           <https://github.com/Perl/perl5/issues/16349>.

       o   Fix for "mutator not seen in (lex = ...) .= ..."  [GH #16655]
           <https://github.com/Perl/perl5/issues/16655>.

       o   "pack "u", "invalid uuencoding"" now properly NUL terminates the
           zero-length SV produced.  [GH #16343]
           <https://github.com/Perl/perl5/issues/16343>.

       o   Improve the debugging output for calloc() calls with "-Dm".  [GH
           #16653] <https://github.com/Perl/perl5/issues/16653>.

       o   Regexp script runs were failing to permit ASCII digits in some
           cases.  [GH #16704] <https://github.com/Perl/perl5/issues/16704>.

       o   On Unix-like systems supporting a platform-specific technique for
           determining $^X, Perl failed to fall back to the generic technique
           when the platform-specific one fails (for example, a Linux system
           with /proc not mounted).  This was a regression in Perl 5.28.0.
           [GH #16715] <https://github.com/Perl/perl5/issues/16715>.

       o   SDBM_File is now more robust with corrupt database files.  The
           improvements do not make SDBM files suitable as an interchange
           format.  [GH #16164] <https://github.com/Perl/perl5/issues/16164>.

       o   "binmode($fh);" or "binmode($fh, ':raw');" now properly removes the
           ":utf8" flag from the default ":crlf" I/O layer on Win32.  [GH
           #16730] <https://github.com/Perl/perl5/issues/16730>.

       o   The experimental reference aliasing feature was misinterpreting
           array and hash slice assignment as being localised, e.g.

               \(@a[3,5,7]) = \(....);

           was being interpreted as:

               local \(@a[3,5,7]) = \(....);

           [GH #16701] <https://github.com/Perl/perl5/issues/16701>.

       o   "sort SUBNAME" within an "eval EXPR" when "EXPR" was UTF-8 upgraded
           could panic if the "SUBNAME" was non-ASCII.  [GH #16979]
           <https://github.com/Perl/perl5/issues/16979>.

       o   Correctly handle realloc() modifying "errno" on success so that the
           modification isn't visible to the perl user, since realloc() is
           called implicitly by the interpreter.  This modification is
           permitted by the C standard, but has only been observed on FreeBSD
           13.0-CURRENT.  [GH #16907]
           <https://github.com/Perl/perl5/issues/16907>.

       o   Perl now exposes POSIX "getcwd" as "Internals::getcwd()" if
           available.  This is intended for use by "Cwd.pm" during
           bootstrapping and may be removed or changed without notice.  This
           fixes some bootstrapping issues while building perl in a directory
           where some ancestor directory isn't readable.  [GH #16903]
           <https://github.com/Perl/perl5/issues/16903>.

       o   "pack()" no longer can return malformed UTF-8.  It croaks if it
           would otherwise return a UTF-8 string that contains malformed
           UTF-8.  This protects against potential security threats.  [GH
           #16035] <https://github.com/Perl/perl5/issues/16035>.

       o   See "Any set of digits in the Common script are legal in a script
           run of another script".

       o   Regular expression matching no longer leaves stale UTF-8 length
           magic when updating $^R. This could result in "length($^R)"
           returning an incorrect value.

       o   Reduce recursion on ops [GH #11866]
           <https://github.com/Perl/perl5/issues/11866>.

           This can prevent stack overflow when processing extremely deep op
           trees.

       o   Avoid leak in multiconcat with overloading.  [GH #16823]
           <https://github.com/Perl/perl5/issues/16823>.

       o   The handling of user-defined "\p{}" properties (see "User-Defined
           Character Properties" in perlunicode) has been rewritten to be in C
           (instead of Perl).  This speeds things up, but in the process
           several inconsistencies and bug fixes are made.

           1.  A few error messages have minor wording changes.  This is
               essentially because the new way is integrated into the regex
               error handling mechanism that marks the position in the input
               at which the error occurred.  That was not possible previously.
               The messages now also contain additional back-trace-like
               information in case the error occurs deep in nested calls.

           2.  A user-defined property is implemented as a perl subroutine
               with certain highly constrained naming conventions.  It was
               documented previously that the sub would be in the current
               package if the package was unspecified.  This turned out not to
               be true in all cases, but now it is.

           3.  All recursive calls are treated as infinite recursion.
               Previously they would cause the interpreter to panic.  Now,
               they cause the regex pattern to fail to compile.

           4.  Similarly, any other error likely would lead to a panic; now to
               just the pattern failing to compile.

           5.  The old mechanism did not detect illegal ranges in the
               definition of the property.  Now, the range max must not be
               smaller than the range min.  Otherwise, the pattern fails to
               compile.

           6.  The intention was to have each sub called only once during the
               lifetime of the program, so that a property's definition is
               immutable.  This was relaxed so that it could be called once
               for all /i compilations, and potentially a second time for
               non-/i (the sub is passed a parameter indicating which).
               However, in practice there were instances when this was broken,
               and multiple calls were possible.  Those have been fixed.  Now
               (besides the /i,non-/i cases) the only way a sub can be called
               multiple times is if some component of it has not been defined
               yet.  For example, suppose we have sub IsA() whose definition
               is known at compile time, and it in turn calls isB() whose
               definition is not yet known.  isA() will be called each time a
               pattern it appears in is compiled.  If isA() also calls isC()
               and that definition is known, isC() will be called just once.

           7.  There were some races and very long hangs should one thread be
               compiling the same property as another simultaneously.  These
               have now been fixed.

       o   Fixed a failure to match properly.

           An EXACTFish regnode has a finite length it can hold for the string
           being matched.  If that length is exceeded, a second node is used
           for the next segment of the string, for as many regnodes as are
           needed.  Care has to be taken where to break the string, in order
           to deal multi-character folds in Unicode correctly. If we want to
           break a string at a place which could potentially be in the middle
           of a multi-character fold, we back off one (or more) characters,
           leaving a shorter EXACTFish regnode. This backing off mechanism
           contained an off-by-one error.  [GH #16806]
           <https://github.com/Perl/perl5/issues/16806>.

       o   A bare "eof" call with no previous file handle now returns true.
           [GH #16786] <https://github.com/Perl/perl5/issues/16786>

       o   Failing to compile a format now aborts compilation.  Like other
           errors in sub-parses this could leave the parser in a strange
           state, possibly crashing perl if compilation continued.  [GH
           #16169] <https://github.com/Perl/perl5/issues/16169>

       o   If an in-place edit is still in progress during global destruction
           and the process exit code (as stored in $?) is zero, perl will now
           treat the in-place edit as successful, replacing the input file
           with any output produced.

           This allows code like:

             perl -i -ne 'print "Foo"; last'

           to replace the input file, while code like:

             perl -i -ne 'print "Foo"; die'

           will not.  Partly resolves [GH #16748]
           <https://github.com/Perl/perl5/issues/16748>.

       o   A regression in 5.28 caused the following code to fail

            close(STDIN); open(CHILD, "|wc -l")'

           because the child's stdin would be closed on exec. This has now
           been fixed.

       o   Fixed an issue where compiling a regexp containing both compile-
           time and run-time code blocks could lead to trying to compile
           something which is invalid syntax.

       o   Fixed build failures with "-DNO_LOCALE_NUMERIC" and
           "-DNO_LOCALE_COLLATE".  [GH #16771]
           <https://github.com/Perl/perl5/issues/16771>.

       o   Prevent the tests in ext/B/t/strict.t from being skipped.  [GH
           #16783] <https://github.com/Perl/perl5/issues/16783>.

       o   "/di" nodes ending or beginning in s are now "EXACTF". We do not
           want two "EXACTFU" to be joined together during optimization, and
           to form a "ss", "sS", "Ss" or "SS" sequence; they are the only
           multi-character sequences which may match differently under "/ui"
           and "/di".


Acknowledgements

       Perl 5.30.0 represents approximately 11 months of development since
       Perl 5.28.0 and contains approximately 620,000 lines of changes across
       1,300 files from 58 authors.

       Excluding auto-generated files, documentation and release tools, there
       were approximately 510,000 lines of changes to 750 .pm, .t, .c and .h
       files.

       Perl continues to flourish into its fourth decade thanks to a vibrant
       community of users and developers. The following people are known to
       have contributed the improvements that became Perl 5.30.0:

       Aaron Crane, Abigail, Alberto Simo~es, Alexandr Savca, Andreas Koenig,
       Andy Dougherty, Aristotle Pagaltzis, Brian Greenfield, Chad Granum,
       Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsaaker, Dan
       Book, Dan Dedrick, Daniel Dragan, Dan Kogai, David Cantrell, David
       Mitchell, Dominic Hargreaves, E. Choroba, Ed J, Eugen Konkov, Francois
       Perrad, Graham Knop, Hauke D, H.Merijn Brand, Hugo van der Sanden,
       Jakub Wilk, James Clarke, James E Keenan, Jerry D. Hedden, Jim Cromie,
       John SJ Anderson, Karen Etheridge, Karl Williamson, Leon Timmermans,
       Matthias Bethke, Nicholas Clark, Nicolas R., Niko Tyni, Pali, Petr
       PisaX, Phil Pearl (Lobbes), Richard Leach, Ryan Voots, Sawyer X, Shlomi
       Fish, Sisyphus, Slaven Rezic, Steve Hay, Sullivan Beck, Tina Mueller,
       Tomasz Konojacki, Tom Wyant, Tony Cook, Unicode Consortium, Yves Orton,
       Zak B. Elep.

       The list above is almost certainly incomplete as it is automatically
       generated from version control history. In particular, it does not
       include the names of most of the (very much appreciated) contributors
       who reported issues to the Perl bug tracker. Noteworthy in this release
       were the large number of bug fixes made possible by Sergey Aleynikov's
       high quality perlbug reports for issues he discovered by fuzzing with
       AFL.

       Many of the changes included in this version originated in the CPAN
       modules included in Perl's core. We're grateful to the entire CPAN
       community for helping Perl to flourish.

       For a more complete list of all of Perl's historical contributors,
       please see the AUTHORS file in the Perl source distribution.


Reporting Bugs

       If you find what you think is a bug, you might check the perl bug
       database at <https://rt.perl.org/>.  There may also be information at
       <http://www.perl.org/>, the Perl Home Page.

       If you believe you have an unreported bug, please run the perlbug
       program included with your release.  Be sure to trim your bug down to a
       tiny but sufficient test case.  Your bug report, along with the output
       of "perl -V", will be sent off to perlbug@perl.org to be analysed by
       the Perl porting team.

       If the bug you are reporting has security implications which make it
       inappropriate to send to a publicly archived mailing list, then see
       "SECURITY VULNERABILITY CONTACT INFORMATION" in perlsec for details of
       how to report the issue.


Give Thanks

       If you wish to thank the Perl 5 Porters for the work we had done in
       Perl 5, you can do so by running the "perlthanks" program:

           perlthanks

       This will send an email to the Perl 5 Porters list with your show of
       thanks.


SEE ALSO

       The Changes file for an explanation of how to view exhaustive details
       on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.



perl v5.34.0                      2021-05-04                PERL5300DELTA(1pm)

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