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perldelta - what is new for perl v5.23.5


This document describes differences between the 5.23.4 release and the 5.23.5 release.

If you are upgrading from an earlier release such as 5.23.3, first read perl5234delta, which describes differences between 5.23.3 and 5.23.4.

Performance Enhancements

  • Faster addition, subtraction and multiplication.

    Since 5.8.0, arithmetic became slower due to the need to support 64-bit integers. To deal with 64-bit integers, a lot more corner cases need to be checked, which adds time. We now detect common cases where there is no need to check for those corner cases, and special-case them.

  • Faster preincrement, predecrement, postincrement, postdecrement.

    By internally splitting the functions which handled multiple cases into different functions.

Modules and Pragmata

Updated Modules and Pragmata

  • arybase has been upgraded from version 0.10 to 0.11.

  • B has been upgraded from version 1.60 to 1.61.

  • base has been upgraded from version 2.22 to 2.22_01.

    Better handling of attempts to load non-existent modules. Improvements to fields.pm documentation. base now requires v5.8.0.

  • Carp has been upgraded from version 1.37 to 1.38.

    Improvements when working with older perls.

  • Config::Perl::V has been upgraded from version 0.24 to 0.25.

  • Devel::Peek has been upgraded from version 1.22 to 1.23.

  • Dumpvalue has been upgraded from version 1.17 to 1.18.

  • DynaLoader has been upgraded from version 1.35 to 1.36.

  • fields has been upgraded from version 2.17 to 2.22_01.

  • File::Find has been upgraded from version 1.31 to 1.32.

    Handles empty directory lists.

  • File::Spec has been upgraded from version 3.58 to 3.59.

  • Getopt::Long has been upgraded from version 2.47 to 2.48.

    Fixes an issue with gnu_compat

  • Hash::Util::FieldHash has been upgraded from version 1.17 to 1.18.

  • IPC::Open3 has been upgraded from version 1.19 to 1.20.

    Include the error message on exec() failure.

  • Math::BigInt has been upgraded from version 1.999704 to 1.999710.

  • Math::BigInt::FastCalc has been upgraded from version 0.34 to 0.37.

  • Module::CoreList has been upgraded from version 5.20151020 to 5.20151120.

  • Module::Metadata has been upgraded from version 1.000029 to 1.000030.

    Temp dirs cleaned up during tests. More accurately mark tests as TODO, so as to have a quieter and less confusing test run without passing TODO tests.

  • PerlIO::encoding has been upgraded from version 0.22 to 0.23.

  • PerlIO::mmap has been upgraded from version 0.014 to 0.015.

  • PerlIO::scalar has been upgraded from version 0.23 to 0.24.

  • PerlIO::via has been upgraded from version 0.15 to 0.16.

  • Pod::Simple has been upgraded from version 3.30 to 3.32.

    Switched debugging output from STDOUT to STDERR.

    Added errata_seen() to make POD errors easily accessible.

    Simplified the detection of case-insensitivity in Pod::Simple::Search.

    Fixed Use of uninitialized value $1 in lc warning in Pod::Simple::Search.

    If @INC includes the current directory symbol, ., the survey() method of Pod::Simple::Search no longer excludes it from its list of directories to search. Instead, The survey() and find() methods now both exclude duplicate directories from @INC (RT #102344).

    Moved source repository and updated links to new perl-pod GitHub organization: https://github.com/perl-pod/pod-simple.

    Improved repository links and added GitHub issue tracking link to the distribution metadata.

    Switched from File::Spec's catdir to catfile for path names, to fix failures on VMS. Also now use Unix path semantics where they're not required to be platform-specific. (RT #105511).

    Improved the example use of the html_encode_chars() method in the Pod::Simple::XHTML documentation.

  • POSIX has been upgraded from version 1.58 to 1.59.

  • Thread::Queue has been upgraded from version 3.06 to 3.07.

  • threads has been upgraded from version 2.03 to 2.04.

  • threads::shared has been upgraded from version 1.48 to 1.49.

  • Tie::Scalar has been upgraded from version 1.03 to 1.04.

  • Time::HiRes has been upgraded from version 1.9727_02 to 1.9728.

  • Time::Piece has been upgraded from version 1.30 to 1.31.

  • Unicode::Normalize has been upgraded from version 1.21 to 1.23.

  • XSLoader has been upgraded from version 0.20 to 0.21.


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.

New Diagnostics

New Errors

Changes to Existing Diagnostics

  • When running out of memory during an attempt the increase the stack size, previously, perl would die using the cryptic message panic: av_extend_guts() negative count (-9223372036854775681). This has been fixed to show the prettier message: Out of memory during stack extend

Configuration and Compilation

  • Configure now acts as if the -O option is always passed, allowing command line options to override saved configuration. This should eliminate confusion when command line options are ignored for no obvious reason. -O is now permitted, but ignored.

  • Some filesystem stat symbols which were not used by the Perl core were removed in an earlier commit. However, since these symbols turned out to be used by at least one CPAN module, these symbols have been restored.

  • PPPort.so/PPPort.dll no longer get installed, as they are not used by PPPort.pm, only by its test files.

  • It is now possible to specify which compilation date to show on perl -V output, by setting the macro PERL_BUILD_DATE.

Platform Support

Platform-Specific Notes


Win32 does now a parallel build with C++.


Workaround where Tru64 balks when prototypes are listed as PERL_STATIC_INLINE, but where the test is build with -DPERL_NO_INLINE_FUNCTIONS.

Internal Changes

  • sv_ref() is now part of the API.

Selected Bug Fixes

  • \b{sb} works much better. In Perl v5.22.0, this new construct didn't seem to give the expected results, yet passed all the tests in the extensive suite furnished by Unicode. It turns out that it was because these were short input strings, and the failures had to do with longer inputs. This was fixed in Perl 5.23.4, but the improvement was not noticed until after that was released, so is included here now.

  • Certain syntax errors in "Extended Bracketed Character Classes" in perlrecharclass caused panics instead of the proper error message. This has now been fixed. [perl #126481]

  • An earlier commit added a message when a quantifier in a regular expression was useless, but then caused the parser to skip it; this caused the surplus quantifier to be silently ignored, instead of throwing an error. This is now fixed. [perl #126253]

  • The switch to building non-XS modules last in win32/makefile.mk (introduced by design as part of the changes to enable parallel building) caused the build of POSIX to break due to problems with the version module. This is now fixed.

  • Improved parsing of hex float constants.

  • Fixed an issue with pack where pack "H" (and pack "h") could read past the source when given a non-utf8 source, and a utf8 target. [perl #126325]

  • Fixed several cases where perl would abort due to a segmentation fault, or a C-level assert. [perl #126615], [perl #126602], [perl #126193].


Perl 5.23.5 represents approximately 4 weeks of development since Perl 5.23.4 and contains approximately 12,000 lines of changes across 290 files from 23 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 6,400 lines of changes to 180 .pm, .t, .c and .h files.

Perl continues to flourish into its third decade thanks to a vibrant community of users and developers. The following people are known to have contributed the improvements that became Perl 5.23.5:

Aaron Crane, Abigail, Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, David Mitchell, Dr.Ruud, H.Merijn Brand, Ivan Pozdeev, James E Keenan, Jarkko Hietaniemi, Jerry D. Hedden, Karen Etheridge, Karl Williamson, Lukas Mai, Mohammed El-Afifi, Niko Tyni, Peter Rabbitson, Reini Urban, Ricardo Signes, Steve Hay, Tony Cook.

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 the (very much appreciated) contributors who reported issues to the Perl bug tracker.

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 articles recently posted to the comp.lang.perl.misc newsgroup and 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 please send it to perl5-security-report@perl.org. This points to a closed subscription unarchived mailing list, which includes all the core committers, who will be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN.


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.