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John SJ Anderson
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perl5291delta - what is new for perl v5.29.1


This document describes differences between the 5.29.0 release and the 5.29.1 release.

If you are upgrading from an earlier release such as 5.28.0, first read perl5290delta, which describes differences between 5.28.0 and 5.29.0.

Incompatible Changes

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.

Performance Enhancements

  • 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.

Modules and Pragmata

Updated Modules and Pragmata

  • bignum has been upgraded from version 0.49 to 0.50.

  • Compress::Raw::Bzip2 has been upgraded from version 2.074 to 2.081.

  • Compress::Raw::Zlib has been upgraded from version 2.076 to 2.081.

  • Config::Perl::V has been upgraded from version 0.29 to 0.30.

  • DB_File has been upgraded from version 1.840 to 1.842.

  • Devel::PPPort has been upgraded from version 3.40 to 3.42.

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

  • experimental has been upgraded from version 0.019 to 0.020.

  • ExtUtils::Manifest has been upgraded from version 1.70 to 1.71.

  • File::Temp has been upgraded from version 0.2304 to 0.2308.

  • IO-Compress has been upgraded from version 2.074 to 2.081.

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

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

  • Math::BigInt has been upgraded from version 1.999811 to 1.999813.

  • Math::BigInt::FastCalc has been upgraded from version 0.5006 to 0.5007.

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

  • Module::CoreList has been upgraded from version 5.20180626 to 5.20180720.

  • parent has been upgraded from version 0.236 to 0.237.

  • perlfaq has been upgraded from version 5.021011 to 5.20180605.

  • podlators has been upgraded from version 4.10 to 4.11.

  • Storable has been upgraded from version 3.08 to 3.11.

  • Test::Simple has been upgraded from version 1.302133 to 1.302138.

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

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

  • version has been upgraded from version 0.9923 to 0.9924.


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.

Additionally, the following selected changes have been made:


  • AvFILL() was wrongly listed as deprecated. This has been corrected. [perl #133278]


  • The behaviour of tr when the delimiter is an apostrophe has been clarified. In particular, hyphens aren't special, and \x{} isn't interpolated. [perl #130679]


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

  • 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/".


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

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.

  • 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).

  • 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.)

Selected Bug Fixes

  • Compilation under -DPERL_MEM_LOG and -DNO_LOCALE have been fixed.

  • 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. [perl #133368]


Perl 5.29.1 represents approximately 3 weeks of development since Perl 5.29.0 and contains approximately 68,000 lines of changes across 510 files from 18 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 62,000 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 5.29.1:

Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, David Mitchell, François Perrad, H.Merijn Brand, Hugo van der Sanden, James E Keenan, Jerry D. Hedden, Jim Cromie, Karen Etheridge, Karl Williamson, Nicholas Clark, Sawyer X, Steve Hay, Tina Müller, Yves Orton.

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://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:


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.