perl5337delta - what is new for perl v5.33.7


This document describes differences between the 5.33.6 release and the 5.33.7 release.

If you are upgrading from an earlier release such as 5.33.5, first read perl5336delta, which describes differences between 5.33.5 and 5.33.6.

Core Enhancements

Experimental Try/Catch Syntax

An initial experimental attempt at providing try/catch notation has been added.

    use feature 'try';

    try {
    catch ($e) {
        warn "An error occurred: $e";

For more information, see "Try Catch Exception Handling" in perlsyn.

Modules and Pragmata

Updated Modules and Pragmata

  • autodie has been upgraded from version 2.32 to 2.34.

  • B::Deparse has been upgraded from version 1.55 to 1.56.

  • ExtUtils::CBuilder has been upgraded from version 0.280235 to 0.280236.

  • ExtUtils::MakeMaker has been upgraded from version 7.58 to 7.60.

  • ExtUtils::PL2Bat has been upgraded from version 0.003 to 0.004.

  • feature has been upgraded from version 1.62 to 1.63.

  • File::Find has been upgraded from version 1.38 to 1.39. Minor documentation touchups only.

  • Hash::Util has been upgraded from version 0.24 to 0.25.

  • IO has been upgraded from version 1.45 to 1.46.

  • JSON::PP has been upgraded from version 4.05 to 4.06.

  • Module::CoreList has been upgraded from version 5.20210120 to 5.20210220.

  • mro has been upgraded from version 1.25 to 1.25_001.

  • Opcode has been upgraded from version 1.49 to 1.50.

  • PerlIO::encoding has been upgraded from version 0.28 to 0.30.

  • Time::HiRes has been upgraded from version 1.9766 to 1.9767.

  • warnings has been upgraded from version 1.50 to 1.51.


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:


  • my() and state() now explicitly warn the reader that lexical variables should typically not be redeclared within the same scope or statement. [GH #18389]


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 perldiag

perldiag was missing some entries for existing diagnostics.

  • Error %s in expansion of %s

    An error was encountered in handling a user-defined property ("User-Defined Character Properties" in perlunicode). These are programmer written subroutines, hence subject to errors that may prevent them from compiling or running.

  • Infinite recursion in user-defined property

    A user-defined property ("User-Defined Character Properties" in perlunicode) can depend on the definitions of other user-defined properties. If the chain of dependencies leads back to this property, infinite recursion would occur, were it not for the check that raised this error.

  • Timeout waiting for another thread to define \p{%s}

    The first time a user-defined property ("User-Defined Character Properties" in perlunicode) is used, its definition is looked up and converted into an internal form for more efficient handling in subsequent uses. There could be a race if two or more threads tried to do this processing nearly simultaneously.

  • Unknown user-defined property name \p{%s}

    You specified to use a property within the \p{...} which was a syntactically valid user-defined property, but no definition was found for it

Configuration and Compilation

  • stadtx hash support has been removed

    stadtx support has been entirely removed. Previously, it could be requested with PERL_HASH_FUNC_STADTX, and was default in 64-bit builds. It has been replaced with SipHash. SipHash has been more rigorously reviewed than stadtx.

Platform Support

Platform-Specific Notes


Building with compilers (version 3.4.5 or later) using mingw runtime versions < 3.22 now works again. This was broken in Perl 5.31.4.

Building with compilers (version 3.4.5 or later) using mingw runtime versions >= 3.21 now works (for compilers up to version 5.3.0)., and thus support for dmake, has been removed. It is still possible to build Perl on Windows using nmake (Makefile) and GNU make (GNUmakefile). [GH #18511]

Selected Bug Fixes

  • pack/unpack format 'D' now works on all systems that could support it

    Previously if NV == long double, now it is supported on all platforms that have long doubles. In particular that means it is now also supported on quadmath platforms.


Kent Fredric (KENTNL) passed away in February 2021. A native of New Zealand and a self-described "huge geek," Kent was the author or maintainer of 178 CPAN distributions, the Perl maintainer for the Gentoo Linux distribution and a contributor to the Perl core distribution. He is mourned by his family, friends and open source software communities worldwide.


Perl 5.33.7 represents approximately 4 weeks of development since Perl 5.33.6 and contains approximately 11,000 lines of changes across 230 files from 19 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 2,800 lines of changes to 140 .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 5.33.7:

Andy Dougherty, Chris 'BinGOs' Williams, Craig A. Berry, Dan Book, Eugene Alvin Villar, H.Merijn Brand, Hugo van der Sanden, James E Keenan, Karl Williamson, Leon Timmermans, Paul Evans, Ricardo Signes, Richard Leach, Sawyer X, Steve Hay, Tomasz Konojacki, Tony Cook, Yves Orton, Zakariyya Mughal.

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.