++ed by:
209 non-PAUSE users
Author image Todd Rinaldo
and 1 contributors


perl5336delta - what is new for perl v5.33.6


This document describes differences between the 5.33.5 release and the 5.33.6 release.

If you are upgrading from an earlier release such as 5.33.4, first read perl5335delta, which describes differences between 5.33.4 and 5.33.5.

Core Enhancements

qr/{,n}/ is now accepted

An empty lower bound is now accepted for regular expression quantifiers, like {,3}.

Blanks freely allowed within but adjacent to curly braces

(in double-quotish contexts and regular expression patterns)

This means you can write things like \x{ FFFC } if you like. This applies to all such constructs, namely \b{}, \g{}, \k{}, \N{}, \o{}, and \x{}; as well as the regular expression quantifier {m,n}. \p{} and \P{} retain their already-existing, even looser, rules mandated by the Unicode standard (see "Properties accessible through \p{} and \P{}" in perluniprops).

This ability is in effect regardless of the presence of the /x regular expression pattern modifier.

Additionally, the comma in a regular expression braced quantifier may have blanks (tabs or spaces) before and/or after the comma, like qr/a{ 5, 7 }/.

Modules and Pragmata

Updated Modules and Pragmata

  • Carp has been upgraded from version 1.51 to 1.52.

  • Compress::Raw::Bzip2 has been upgraded from version 2.096 to 2.100.

  • Compress::Raw::Zlib has been upgraded from version 2.096 to 2.100.

  • DynaLoader has been upgraded from version 1.49 to 1.50.

  • ExtUtils::MakeMaker has been upgraded from version 7.56 to 7.58.

  • ExtUtils::Manifest has been upgraded from version 1.72 to 1.73.

  • feature has been upgraded from version 1.61 to 1.62.

    Added the default enabled bareword_filehandles feature.

  • GDBM_File has been upgraded from version 1.18 to 1.19.

    New functions and compatibility for newer versions of GDBM. [GH #18435]

  • IO has been upgraded from version 1.44 to 1.45.

    IO::Socket now stores error messages in $IO::Socket::errstr, in addition to in $@.

  • IO-Compress has been upgraded from version 2.096 to 2.100.

  • libnet has been upgraded from version 3.12 to 3.13.

  • Module::CoreList has been upgraded from version 5.20201220 to 5.20210120.

  • POSIX has been upgraded from version 1.96 to 1.97.

    POSIX::signbit() behaviour has been improved. [GH #18441]

    Documentation for asctime clarifies that the result is always in English. (Use strftime for a localized result.)

  • Socket has been upgraded from version 2.030 to 2.031.

  • warnings has been upgraded from version 1.49 to 1.50.

  • XS::APItest has been upgraded from version 1.14 to 1.15.


New Documentation


This document describes the goals, scope, system, and rules for Perl's new governance model.

Other pod files, most notably perlpolicy, were amended to reflect its adoption.

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, open an issue at https://github.com/Perl/perl5/issues.

Additionally, the following selected changes have been made:


  • The freenode IRC URL has been updated.


  • The localtime entry has been improved and now also states that the result of the function is always in English.


  • A new example shows how a lexical my variable can be declared during the initialization of a for loop.


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

Configuration and Compilation

  • Configure

    A new probe checks for buggy libc implementations of the gcvt/qgcvt functions. [GH #18170]


Tests were added and changed to reflect the other additions and changes in this release. Furthermore, these significant changes were made:

  • t/re/opt.t was added, providing a test harness for regexp optimization. [GH #18213]

  • A workaround for CPAN distributions needing dot in @INC has been removed [GH #18394]. All distributions that previously required the workaround have now been adapted.

Platform Support

Platform-Specific Notes

Mac OS X

A number of system libraries no longer exist as actual files on Big Sur, even though dlopen will pretend they do, so now we fall back to dlopen if a library file can not be found. [GH #18407]

MS Windows

perl can now be built with USE_QUADMATH on MS Windows using (32-bit and 64-bit) mingw-w64 ports of gcc. [GH #18465]

The pl2bat.pl utility now needs to use ExtUtils::PL2Bat. This could cause failures in parallel builds.

Selected Bug Fixes

  • Skip trying to constant fold an incomplete op tree [GH #18380]

    Constant folding of chained comparison op trees could fail under certain conditions, causing perl to crash. As a quick fix, constant folding is now skipped for such op trees. This also addresses [GH #17917].

  • %g formatting broken on Ubuntu-18.04, NVSIZE == 8 [GH #18170]

    Buggy libc implementations of the gcvt and qgcvt functions caused (s)printf to incorrectly truncate %g formatted numbers. A new Configure probe now checks for this, with the result that the libc sprintf will be used in place of gcvt and qgcvt.

    Tests added as part of this fix also revealed related problems in some Windows builds. The makefiles for MINGW builds on Windows have thus been adjusted to use USE_MINGW_ANSI_STDIO by default, ensuring that they also provide correct (s)printf formatting of numbers.

  • op.c: croak on "my $_" when "use utf8" is in effect [GH #18449]

    The lexical topic feature experiment was removed in Perl v5.24 and declaring my $_ became a compile time error. However, it was previously still possible to make this declaration if use utf8 was in effect.

  • regexec.c: Fix assertion failure [GH #18451]

    Fuzzing triggered an assertion failure in the regexp engine when too many characters were copied into a buffer.


Perl 5.33.6 represents approximately 4 weeks of development since Perl 5.33.5 and contains approximately 96,000 lines of changes across 450 files from 26 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 85,000 lines of changes to 320 .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 5.33.6:

Branislav Zahradník, Chris 'BinGOs' Williams, Craig A. Berry, Dan Book, Daniel Böhmer, Daniel Laügt, Felipe Gasper, Hugo van der Sanden, James E Keenan, Kang-min Liu, Karen Etheridge, Karl Williamson, Leon Timmermans, Max Maischein, Michael G Schwern, Paul Evans, Ricardo Signes, Richard Leach, Sawyer X, Sergey Poznyakoff, Sisyphus, Steve Hay, TAKAI Kousuke, Tomasz Konojacki, Tom Hukins, 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 perl bug database at https://github.com/Perl/perl5/issues. There may also be information at http://www.perl.org/, the Perl Home Page.

If you believe you have an unreported bug, please open an issue at https://github.com/Perl/perl5/issues. Be sure to trim your bug down to a tiny but sufficient test case.

If the bug you are reporting has security implications which make it inappropriate to send to a public issue tracker, 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:


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


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.