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+=encoding utf8
+
+=head1 NAME
+
+perl5201delta - what is new for perl v5.20.1
+
+=head1 DESCRIPTION
+
+This document describes differences between the 5.20.0 release and the 5.20.1
+release.
+
+If you are upgrading from an earlier release such as 5.18.0, first read
+L<perl5200delta>, which describes differences between 5.18.0 and 5.20.0.
+
+=head1 Incompatible Changes
+
+There are no changes intentionally incompatible with 5.20.0.  If any exist,
+they are bugs, and we request that you submit a report.  See L</Reporting Bugs>
+below.
+
+=head1 Performance Enhancements
+
+=over 4
+
+=item *
+
+An optimization to avoid problems with COW and deliberately overallocated PVs
+has been disabled because it interfered with another, more important,
+optimization, causing a slowdown on some platforms.
+L<[perl #121975]|https://rt.perl.org/Ticket/Display.html?id=121975>
+
+=item *
+
+Returning a string from a lexical variable could be slow in some cases.  This
+has now been fixed.
+L<[perl #121977]|https://rt.perl.org/Ticket/Display.html?id=121977>
+
+=back
+
+=head1 Modules and Pragmata
+
+=head2 Updated Modules and Pragmata
+
+=over 4
+
+=item *
+
+L<Config::Perl::V> has been upgraded from version 0.20 to 0.22.
+
+The list of Perl versions covered has been updated and some flaws in the
+parsing have been fixed.
+
+=item *
+
+L<Exporter> has been upgraded from version 5.70 to 5.71.
+
+Illegal POD syntax in the documentation has been corrected.
+
+=item *
+
+L<ExtUtils::CBuilder> has been upgraded from version 0.280216 to 0.280217.
+
+Android builds now link to both B<-lperl> and C<$Config::Config{perllibs}>.
+
+=item *
+
+L<File::Copy> has been upgraded from version 2.29 to 2.30.
+
+The documentation now notes that C<copy> will not overwrite read-only files.
+
+=item *
+
+L<Module::CoreList> has been upgraded from version 3.11 to 5.020001.
+
+The list of Perl versions covered has been updated.
+
+=item *
+
+The PathTools module collection has been upgraded from version 3.47 to 3.48.
+
+Fallbacks are now in place when cross-compiling for Android and
+C<$Config::Config{sh}> is not yet defined.
+L<[perl #121963]|https://rt.perl.org/Ticket/Display.html?id=121963>
+
+=item *
+
+L<PerlIO::via> has been upgraded from version 0.14 to 0.15.
+
+A minor portability improvement has been made to the XS implementation.
+
+=item *
+
+L<Unicode::UCD> has been upgraded from version 0.57 to 0.58.
+
+The documentation includes many clarifications and fixes.
+
+=item *
+
+L<utf8> has been upgraded from version 1.13 to 1.13_01.
+
+The documentation has some minor formatting improvements.
+
+=item *
+
+L<version> has been upgraded from version 0.9908 to 0.9909.
+
+External libraries and Perl may have different ideas of what the locale is.
+This is problematic when parsing version strings if the locale's numeric
+separator has been changed.  Version parsing has been patched to ensure it
+handles the locales correctly.
+L<[perl #121930]|https://rt.perl.org/Ticket/Display.html?id=121930>
+
+=back
+
+=head1 Documentation
+
+=head2 Changes to Existing Documentation
+
+=head3 L<perlapi>
+
+=over 4
+
+=item *
+
+C<av_len> - Emphasize that this returns the highest index in the array, not the
+size of the array.
+L<[perl #120386]|https://rt.perl.org/Ticket/Display.html?id=120386>
+
+=item *
+
+Note that C<SvSetSV> doesn't do set magic.
+
+=item *
+
+C<sv_usepvn_flags> - Fix documentation to mention the use of C<NewX> instead of
+C<malloc>.
+L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
+
+=item *
+
+Clarify where C<NUL> may be embedded or is required to terminate a string.
+
+=back
+
+=head3 L<perlfunc>
+
+=over 4
+
+=item *
+
+Clarify the meaning of C<-B> and C<-T>.
+
+=item *
+
+C<-l> now notes that it will return false if symlinks aren't supported by the
+file system.
+L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
+
+=item *
+
+Note that C<each>, C<keys> and C<values> may produce different orderings for
+tied hashes compared to other perl hashes.
+L<[perl #121404]|https://rt.perl.org/Ticket/Display.html?id=121404>
+
+=item *
+
+Note that C<exec LIST> and C<system LIST> may fall back to the shell on Win32.
+Only C<exec PROGRAM LIST> and C<system PROGRAM LIST> indirect object syntax
+will reliably avoid using the shell.  This has also been noted in L<perlport>.
+L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
+
+=item *
+
+Clarify the meaning of C<our>.
+L<[perl #122132]|https://rt.perl.org/Ticket/Display.html?id=122132>
+
+=back
+
+=head3 L<perlguts>
+
+=over 4
+
+=item *
+
+Explain various ways of modifying an existing SV's buffer.
+L<[perl #116925]|https://rt.perl.org/Ticket/Display.html?id=116925>
+
+=back
+
+=head3 L<perlpolicy>
+
+=over 4
+
+=item *
+
+We now have a code of conduct for the I<< p5p >> mailing list, as documented in
+L<< perlpolicy/STANDARDS OF CONDUCT >>.
+
+=back
+
+=head3 L<perlre>
+
+=over 4
+
+=item *
+
+The C</x> modifier has been clarified to note that comments cannot be continued
+onto the next line by escaping them.
+
+=back
+
+=head3 L<perlsyn>
+
+=over 4
+
+=item *
+
+Mention the use of empty conditionals in C<for>/C<while> loops for infinite
+loops.
+
+=back
+
+=head3 L<perlxs>
+
+=over 4
+
+=item *
+
+Added a discussion of locale issues in XS code.
+
+=back
+
+=head1 Diagnostics
+
+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 L<perldiag>.
+
+=head2 Changes to Existing Diagnostics
+
+=over 4
+
+=item *
+
+L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
+
+Information about Unicode behaviour has been added.
+
+=back
+
+=head1 Configuration and Compilation
+
+=over 4
+
+=item *
+
+Building Perl no longer writes to the source tree when configured with
+F<Configure>'s B<-Dmksymlinks> option.
+L<[perl #121585]|https://rt.perl.org/Ticket/Display.html?id=121585>
+
+=back
+
+=head1 Platform Support
+
+=head2 Platform-Specific Notes
+
+=over 4
+
+=item Android
+
+Build support has been improved for cross-compiling in general and for Android
+in particular.
+
+=item OpenBSD
+
+Corrected architectures and version numbers used in configuration hints when
+building Perl.
+
+=item Solaris
+
+B<c99> options have been cleaned up, hints look for B<solstudio> as well as
+B<SUNWspro>, and support for native C<setenv> has been added.
+
+=item VMS
+
+An old bug in feature checking, mainly affecting pre-7.3 systems, has been
+fixed.
+
+=item Windows
+
+C<%I64d> is now being used instead of C<%lld> for MinGW.
+
+=back
+
+=head1 Internal Changes
+
+=over 4
+
+=item *
+
+Added L<perlapi/sync_locale>.
+Changing the program's locale should be avoided by XS code.  Nevertheless,
+certain non-Perl libraries called from XS, such as C<Gtk> do so.  When this
+happens, Perl needs to be told that the locale has changed.  Use this function
+to do so, before returning to Perl.
+
+=back
+
+=head1 Selected Bug Fixes
+
+=over 4
+
+=item *
+
+A bug has been fixed where zero-length assertions and code blocks inside of a
+regex could cause C<pos> to see an incorrect value.
+L<[perl #122460]|https://rt.perl.org/Ticket/Display.html?id=122460>
+
+=item *
+
+Using C<s///e> on tainted utf8 strings could issue bogus "Malformed UTF-8
+character (unexpected end of string)" warnings.  This has now been fixed.
+L<[perl #122148]|https://rt.perl.org/Ticket/Display.html?id=122148>
+
+=item *
+
+C<system> and friends should now work properly on more Android builds.
+
+Due to an oversight, the value specified through B<-Dtargetsh> to F<Configure>
+would end up being ignored by some of the build process.  This caused perls
+cross-compiled for Android to end up with defective versions of C<system>,
+C<exec> and backticks: the commands would end up looking for F</bin/sh> instead
+of F</system/bin/sh>, and so would fail for the vast majority of devices,
+leaving C<$!> as C<ENOENT>.
+
+=item *
+
+Many issues have been detected by L<Coverity|http://www.coverity.com/> and 
+fixed.
+
+=back
+
+=head1 Acknowledgements
+
+Perl 5.20.1 represents approximately 4 months of development since Perl 5.20.0
+and contains approximately 12,000 lines of changes across 170 files from 36
+authors.
+
+Excluding auto-generated files, documentation and release tools, there were
+approximately 2,600 lines of changes to 110 .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 5.20.1:
+
+Aaron Crane, Abigail, Alberto Simões, Alexandr Ciornii, Alexandre (Midnite)
+Jousset, Andrew Fresh, Andy Dougherty, Brian Fraser, Chris 'BinGOs' Williams,
+Craig A. Berry, Daniel Dragan, David Golden, David Mitchell, H.Merijn Brand,
+James E Keenan, Jan Dubois, Jarkko Hietaniemi, John Peacock, kafka, Karen
+Etheridge, Karl Williamson, Lukas Mai, Matthew Horsfall, Michael Bunk, Peter
+Martini, Rafael Garcia-Suarez, Reini Urban, Ricardo Signes, Shirakata Kentaro,
+Smylers, Steve Hay, Thomas Sibley, Todd Rinaldo, Tony Cook, Vladimir Marek,
+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 F<AUTHORS> file in the Perl source distribution.
+
+=head1 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 L<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 C<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.
+
+=head1 SEE ALSO
+
+The F<Changes> file for an explanation of how to view exhaustive details on
+what changed.
+
+The F<INSTALL> file for how to build Perl.
+
+The F<README> file for general stuff.
+
+The F<Artistic> and F<Copying> files for copyright information.
+
+=cut