The Perl Advent Calendar needs more articles for 2022. Submit your idea today!


perl5331delta - what is new for perl v5.33.1


This document describes differences between the 5.33.0 release and the 5.33.1 release.

If you are upgrading from an earlier release such as 5.32.0, first read perl5330delta, which describes differences between 5.32.0 and 5.33.0.

Modules and Pragmata

New Modules and Pragmata

  • ExtUtils::PL2Bat 0.002 has been added to the Perl core.

    This module is a generalization of the pl2bat script. It being a script has led to at least two forks of this code, this modules will unify them under one implementation with tests.

Updated Modules and Pragmata

  • B has been upgraded from version 1.80 to 1.81.

  • B::Deparse has been upgraded from version 1.54 to 1.55.

  • Data::Dumper has been upgraded from version 2.174 to 2.175.

  • Devel::Peek has been upgraded from version 1.28 to 1.29.

  • Devel::PPPort has been upgraded from version 3.57 to 3.60.

    New PERL_VERSION_* comparison macros are now available.

    ppport.h --api-info no longer includes non-API info unless that is the only match

  • DynaLoader has been upgraded from version 1.47 to 1.48.

  • Errno has been upgraded from version 1.30 to 1.31.

  • Exporter has been upgraded from version 5.74 to 5.75.

  • ExtUtils::Miniperl has been upgraded from version 1.09 to 1.10.

  • ExtUtils::ParseXS has been upgraded from version 3.40 to 3.41.

  • Fcntl has been upgraded from version 1.13 to 1.14.

  • feature has been upgraded from version 1.59 to 1.60.

    A new multidimensional feature has been added, which is enabled by default but allows turning off multi-dimensional array emulation.

  • File::Path has been upgraded from version 2.16 to 2.17.

  • Hash::Util has been upgraded from version 0.23 to 0.24.

  • Hash::Util::FieldHash has been upgraded from version 1.20 to 1.21.

  • IO has been upgraded from version 1.43 to 1.44.

    The error method now reports the error state for both the input and output streams for sockets and character devices. Similarly clearerr now clears the error state for both streams.

    A spurious error reported for regular file handles has been fixed in IO::Handle. GH #18019

  • IPC::SysV has been upgraded from version 2.07 to 2.08.

  • JSON::PP has been upgraded from version 4.04 to 4.05.

  • Math::Complex has been upgraded from version 1.5901 to 1.5902.

  • Module::CoreList has been upgraded from version 5.20200717 to 5.20200820.

  • mro has been upgraded from version 1.23 to 1.24.

  • Net::Ping has been upgraded from version 2.72 to 2.73_01.

  • PerlIO::mmap has been upgraded from version 0.016 to 0.017.

  • Pod::Usage has been upgraded from version 1.69 to 1.70.

  • POSIX has been upgraded from version 1.94 to 1.95.

  • Safe has been upgraded from version 2.41 to 2.42.

  • Socket has been upgraded from version 2.029 to 2.030.

  • Storable has been upgraded from version 3.21 to 3.22.

  • strict has been upgraded from version 1.11 to 1.12.

  • threads has been upgraded from version 2.25 to 2.26.

  • threads::shared has been upgraded from version 1.61 to 1.62.

  • Time::HiRes has been upgraded from version 1.9764 to 1.9765.

  • Unicode::Normalize has been upgraded from version 1.27 to 1.28.

  • warnings has been upgraded from version 1.47 to 1.48.

  • XS::APItest has been upgraded from version 1.09 to 1.11.

  • XS::Typemap has been upgraded from version 0.17 to 0.18.


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

Additionally, the following selected changes have been made:


  • Corrected the description of the scalar ${"_<$filename"} variables.


  • Better explanation of what happens when sleep is called with a zero or negative value.


  • Corrected my_rpeep example in perlguts.

  • A section has been added on the formatted printing of special sizes.


  • The <> and <<>> operators are commonly referred to as the diamond and double diamond operators respectively, but that wasn't mentioned previously in their documentation.

  • Document range op behavior change.


  • Incorrect variables used in an example have been fixed.


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

  • Use of uninitialized value%s

    This warning may now include the array or hash index when the uninitialized value is the result of an element not found. This will only happen if the index is a simple non-magical variable.

Utility Changes (the debugger)

  • New option: HistItemMinLength

    This option controls the minimum length a command must be to get stored in history. Traditionally, this has been fixed at 2. Changes to the debugger are often perilous, and new bugs should be reported so the debugger can be debugged.

  • Fix to i and l commands

    The i $var and l $var commands work again with lexical variables.

Configuration and Compilation

  • The minimum supported Bison version is now 2.4, and the maxiumm is 3.7.

  • Newer 64-bit versions of the Intel C/C++ compiler are now recognised and have the correct flags set.


Tests were added and changed to reflect the other additions and changes in this release.

Platform Support

New Platforms


Allow building Perl on i386 9front systems (fork of plan9).

Updated Platforms


Improve support for Plan9 on i386 platforms.

MacOS (Darwin)

The hints file for darwin has been updated to handle future MacOS versions beyond 10. GH #17946

Discontinued Platforms


Support code relating to Symbian has been removed. Symbian was an operating system for mobile devices. The port was last updated in July 2009, and the platform itself in October 2012.

Platform-Specific Notes


The locale categories LC_SYNTAX and LC_TOD are now recognized. Perl doesn't do anything with these, except it now allows you to specify them. They are included in LC_ALL.

Internal Changes

  • The PERL_GLOBAL_STRUCT compilation option has been removed, and with it the need or the dVAR macro. dVAR remains defined as a no-op outside PERL_CORE for backwards compatiblity with XS modules.

  • A new savestack type SAVEt_HINTS_HH has been added, which neatens the previous behaviour of SAVEt_HINTS. On previous versions the types and values pushed to the save stack would depend on whether the hints included the HINT_LOCALIZE_HH bit, which complicates external code that inspects the save stack. The new version uses a different savestack type to indicate the difference.

  • A new API function "av_count" in perlapi has been added which gives a clearly named way to find how many elements are in an array.

Selected Bug Fixes

  • On Win32, waitpid(-1, WNOHANG) could sometimes have a very large timeout. GH #16529

  • MARK and hence items are now correctly initialized in BOOT XSUBs.

  • Some list assignments involving undef on the left-hand side were over-optimized and produced incorrect results. GH #16685, GH #17816


Perl 5.33.1 represents approximately 5 weeks of development since Perl 5.33.0 and contains approximately 37,000 lines of changes across 740 files from 34 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 11,000 lines of changes to 290 .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 5.33.1:

Adam Hartley, Christian Walde (Mithaldu), Dagfinn Ilmari Mannsåker, Dan Book, David Mitchell, E. Choroba, Graham Knop, Graham Ollis, Hauke D, Ivan Baidakou, James E Keenan, John Lightsey, Karen Etheridge, Karl Williamson, Leon Timmermans, Nicolas R., Paul Evans, Petr Písař, raiph, Renee Baecker, Ricardo Signes, Richard Leach, Romano, Ryan Voots, Samuel Thibault, Sawyer X, Scott Baker, Sizhe Zhao, Thibault Duponchelle, Todd Rinaldo, Tomasz Konojacki, Tom Stellard, Tony Cook, vividsnow.

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 There may also be information at, the Perl Home Page.

If you believe you have an unreported bug, please open an issue at 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.