New perldelta.

10 files changed, 596 insertions, 174 deletions

diff --git a/MANIFEST b/MANIFEST
index d747c744e3..1bb915fa85 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -4440,6 +4440,7 @@ pod/perl5182delta.pod		Perl changes in version 5.18.2
 pod/perl5200delta.pod		Perl changes in version 5.20.0
 pod/perl5210delta.pod		Perl changes in version 5.21.0
 pod/perl5211delta.pod		Perl changes in version 5.21.1
+pod/perl5212delta.pod		Perl changes in version 5.21.2
 pod/perl561delta.pod		Perl changes in version 5.6.1
 pod/perl56delta.pod		Perl changes in version 5.6
 pod/perl581delta.pod		Perl changes in version 5.8.1
diff --git a/Makefile.SH b/Makefile.SH
index 703e5f97b8..ff0b5136c8 100755
--- a/Makefile.SH
+++ b/Makefile.SH
@@ -489,7 +489,7 @@ mini_obj = $(minindt_obj) $(MINIDTRACE_O)
 ndt_obj = $(obj0) $(obj1) $(obj2) $(obj3) $(ARCHOBJS)
 obj = $(ndt_obj) $(DTRACE_O)
 
-perltoc_pod_prereqs = extra.pods pod/perl5212delta.pod pod/perlapi.pod pod/perlintern.pod pod/perlmodlib.pod pod/perluniprops.pod
+perltoc_pod_prereqs = extra.pods pod/perl5213delta.pod pod/perlapi.pod pod/perlintern.pod pod/perlmodlib.pod pod/perluniprops.pod
 generated_pods = pod/perltoc.pod $(perltoc_pod_prereqs)
 generated_headers = uudmap.h bitcount.h mg_data.h
 
@@ -999,9 +999,9 @@ pod/perlintern.pod: $(MINIPERL_EXE) autodoc.pl embed.fnc
 pod/perlmodlib.pod: $(MINIPERL_EXE) pod/perlmodlib.PL MANIFEST
 	$(MINIPERL) pod/perlmodlib.PL -q
 
-pod/perl5212delta.pod: pod/perldelta.pod
-	$(RMS) pod/perl5212delta.pod
-	$(LNS) perldelta.pod pod/perl5212delta.pod
+pod/perl5213delta.pod: pod/perldelta.pod
+	$(RMS) pod/perl5213delta.pod
+	$(LNS) perldelta.pod pod/perl5213delta.pod
 
 extra.pods: $(MINIPERL_EXE)
 	-@test ! -f extra.pods || rm -f `cat extra.pods`
diff --git a/pod/.gitignore b/pod/.gitignore
index 5e940fb2ac..63b25c41c6 100644
--- a/pod/.gitignore
+++ b/pod/.gitignore
@@ -53,7 +53,7 @@
 /roffitall
 
 # generated
-/perl5212delta.pod
+/perl5213delta.pod
 /perlapi.pod
 /perlintern.pod
 *.html
diff --git a/pod/perl.pod b/pod/perl.pod
index 0e9fd05eab..5599bc29d5 100644
--- a/pod/perl.pod
+++ b/pod/perl.pod
@@ -179,6 +179,7 @@ aux a2p c2ph h2ph h2xs perlbug pl2pm pod2html pod2man s2p splain xsubpp
 
     perlhist		Perl history records
     perldelta		Perl changes since previous version
+    perl5212delta Perl changes in version 5.21.2
     perl5211delta Perl changes in version 5.21.1
     perl5210delta Perl changes in version 5.21.0
     perl5200delta Perl changes in version 5.20.0
diff --git a/pod/perl5212delta.pod b/pod/perl5212delta.pod
new file mode 100644
index 0000000000..f31a7825c8
--- /dev/null
+++ b/pod/perl5212delta.pod
@@ -0,0 +1,377 @@
+=encoding utf8
+
+=head1 NAME
+
+perl5212delta - what is new for perl v5.21.2
+
+=head1 DESCRIPTION
+
+This document describes differences between the 5.21.1 release and the 5.21.2
+release.
+
+If you are upgrading from an earlier release such as 5.21.0, first read
+L<perl5211delta>, which describes differences between 5.21.0 and 5.21.1.
+
+=head1 Core Enhancements
+
+=head2 Better heuristics on older platforms for determining locale UTF8ness
+
+On platforms that implement neither the C99 standard nor the POSIX 2001
+standard, determining if the current locale is UTF8 or not depends on
+heuristics.  These are improved in this release.
+
+=head1 Security
+
+=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available
+
+The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
+gcc 4.*, is now always used for compiling Perl, if available.
+
+Note that this isn't necessarily a huge step since in many platforms
+the step had already been taken several years ago: many Linux
+distributions (like Fedora) have been using this option for Perl,
+and OS X has enforced the same for many years.
+
+
+=head1 Deprecations
+
+=head2 C<< /\C/ >> character class
+
+This character class, which matches a single byte, even if it appears
+in a multi-byte character has been deprecated. Matching single bytes
+in a multi-byte character breaks encapsulation, and can corrupt utf8
+strings.
+
+=head1 Performance Enhancements
+
+=over 4
+
+=item *
+
+Refactoring of C<< pp_tied >> and CC<< pp_ref >> for small improvements.
+
+=item *
+
+Pathtools don't try to load XS on miniperl.
+
+=item *
+
+A typo fix reduces the size of the C<< OP >> structure.
+
+=item *
+
+Hash lookups where the key is a constant is faster.
+
+=back
+
+=head1 Modules and Pragmata
+
+=head2 Updated Modules and Pragmata
+
+=over 4
+
+=item *
+
+L<arybase> has been upgraded from version 0.07 to 0.08.
+
+=item *
+
+L<B> has been upgraded from version 1.49 to 1.50.
+
+=item *
+
+L<Devel::Peek> has been upgraded from version 1.17 to 1.18.
+
+=item *
+
+L<experimental> has been upgraded from version 0.007 to 0.008.
+
+=item *
+
+L<ExtUtils::Manifest> has been upgraded from version 1.63 to 1.64.
+
+=item *
+
+L<File::Copy> has been upgraded from version 2.29 to 2.30.
+
+=item *
+
+The PathTools module collection (L<File::Spec> and friends) has been
+upgraded from version 3.48 to 3.49.
+
+=item *
+
+L<Filter::Simple> has been upgraded from version 0.91 to 0.92.
+
+=item *
+
+L<Hash::Util> has been upgraded from version 0.17 to 0.18.
+
+=item *
+
+L<IO> has been upgraded from version 1.32 to 1.33.
+
+=item *
+
+L<IO::Socket::IP> has been upgraded from version 0.29 to 0.31.
+
+A better fix for subclassing C<connect()>.
+L<[cpan #95983]|https://rt.cpan.org/Ticket/Display.html?id=95983>
+L<[cpan #97050]|https://rt.cpan.org/Ticket/Display.html?id=97050>
+
+=item *
+
+L<IPC::Open3> has been upgraded from version 1.16 to 1.17.
+
+=item *
+
+L<Math::BigInt> has been upgraded from version 1.9995 to 1.9996.
+
+Correct handling of subclasses.
+L<[cpan #96254]|https://rt.cpan.org/Ticket/Display.html?id=96254>
+L<[cpan #96329]|https://rt.cpan.org/Ticket/Display.html?id=96329>
+
+=item *
+
+L<Module::CoreList> has been upgraded from version 5.021001_01 to 5.021002.
+
+=item *
+
+L<Pod::Usage> has been upgraded from version 1.63 to 1.64.
+
+=item *
+
+L<POSIX> has been upgraded from version 1.40 to 1.41.
+
+=item *
+
+L<threads> has been upgraded from version 1.94 to 1.95.
+
+=item *
+
+L<warnings> has been upgraded from version 1.24 to 1.26.
+
+=back
+
+=head1 Documentation
+
+=head2 Changes to Existing Documentation
+
+=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<< perlfunc >>
+
+=over 4
+
+=item *
+
+Improve documentation of C<< our >>.
+
+=back
+
+=head3 L<< perlsyn >>
+
+=over 4
+
+=item *
+
+The empty conditional in C<< for >> and C<< while >> is now documented
+in L<< perlsyn >>.
+
+=back
+
+=head1 Diagnostics
+
+=head2 New Diagnostics
+
+=head3 New Warnings
+
+=over 4
+
+=item *
+
+L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
+as 0 in increment (++)">
+
+(W numeric) The indicated string was fed as an argument to the C<++> operator
+which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
+See L<perlop/Auto-increment and Auto-decrement> for details.
+
+=item *
+
+L<Redundant argument in %s|perldiag/Redundant argument in %s>
+
+(W redundant) You called a function with more arguments than other
+arguments you supplied indicated would be needed. Currently only
+emitted when a printf-type format required fewer arguments than were
+supplied, but might be used in the future for e.g. L<perlfunc/pack>.
+
+The warnings category C<< redundant >> is new. See also [RT #121025]
+
+=back
+
+=head1 Configuration and Compilation
+
+=over 4
+
+=item *
+
+A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
+see the discussion below at L<< /Internal Changes >>.
+
+=back
+
+=head1 Testing
+
+=over 4
+
+=item *
+
+C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
+more compatible with C<< Test::More >>.
+
+=back
+
+=head1 Platform Support
+
+=head2 Platform-Specific Notes
+
+=over 4
+
+=item Solaris
+
+Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
+didn't follow implied dependencies to build C<perldtrace.h>.  Added an
+explicit dependency to C<depend>.
+L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>
+
+=back
+
+=head1 Internal Changes
+
+=over 4
+
+=item *
+
+The following private API functions had their context parameter removed,
+C<Perl_cast_ulong>,  C<Perl_cast_i32>, C<Perl_cast_iv>,    C<Perl_cast_uv>,
+C<Perl_cv_const_sv>, C<Perl_mg_find>,  C<Perl_mg_findext>, C<Perl_mg_magical>,
+C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
+
+Users of the public API prefix-less calls remain unaffected.
+
+=item *
+
+Experimental support for ops in the optree to be able to locate their
+parent, if any. A general-purpose function, C<< op_sibling_splice() >>
+allows for general manipulating an C<< op_sibling >> chain. The last op
+in such a chain is now marked with the field C<< op_lastsib >>.
+
+A new build define, C<< -DPERL_OP_PARENT >> has been added; if
+given, it forces the core to use C<< op_lastsib >> to detect the
+last sibling in a chain, freeing the last C<< op_sibling >> pointer,
+which then points back to the parent (instead of being C<< NULL >>).
+
+A C-level C<< op_parent() >> function, and a C<< B >> C<< parent() >> method
+have been added; under a default build, they return C<< NULL >>, but when
+C<< -DPERL_OP_PARENT >> has been set, they return the parent of the current op.
+
+=back
+
+=head1 Selected Bug Fixes
+
+=over 4
+
+=item *
+
+C<< s///e >> on tainted utf8 strings got C<< pos() >> messed up. This bug,
+introduced in 5.20, is now fixed. [RT #122148]
+
+=item *
+
+A non-word boundary in a regular expression (C<< \B >>) did not always
+match the end of the string; in particular C<< q{} =~ /\B/ >> did not
+match. This bug, introduced in perl 5.14, is now fixed. [RT #122090]
+
+=item *
+
+C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
+[RT #122171].
+
+=back
+
+=head1 Acknowledgements
+
+Perl 5.21.2 represents approximately 4 weeks of development since Perl 5.21.1
+and contains approximately 11,000 lines of changes across 220 files from 27
+authors.
+
+Excluding auto-generated files, documentation and release tools, there were
+approximately 5,700 lines of changes to 140 .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 5.21.2:
+
+Aaron Crane, Abhijit Menon-Sen, Abigail, Alexandr Ciornii, brian d foy, Brian
+Fraser, Chris 'BinGOs' Williams, Craig A. Berry, Daniel Dragan, David Golden,
+David Mitchell, Dmitri Tikhonov, George Greer, H.Merijn Brand, James E Keenan,
+Jarkko Hietaniemi, Karen Etheridge, Karl Williamson, Matthew Horsfall, Peter
+John Acklam, Peter Martini, Reini Urban, Ricardo Signes, Steve Hay, Tony Cook,
+Yves Orton, Ævar Arnfjörð Bjarmason.
+
+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
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index 974a62c58a..ef88d0bde3 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -2,344 +2,383 @@
 
 =head1 NAME
 
-perldelta - what is new for perl v5.21.2
+[ this is a template for a new perldelta file.  Any text flagged as XXX needs
+to be processed before release. ]
+
+perldelta - what is new for perl v5.21.3
 
 =head1 DESCRIPTION
 
-This document describes differences between the 5.21.1 release and the 5.21.2
+This document describes differences between the 5.21.2 release and the 5.21.3
 release.
 
-If you are upgrading from an earlier release such as 5.21.0, first read
-L<perl5211delta>, which describes differences between 5.21.0 and 5.21.1.
+If you are upgrading from an earlier release such as 5.21.1, first read
+L<perl5212delta>, which describes differences between 5.21.1 and 5.21.2.
+
+=head1 Notice
+
+XXX Any important notices here
 
 =head1 Core Enhancements
 
-=head2 Better heuristics on older platforms for determining locale UTF8ness
+XXX New core language features go here.  Summarize user-visible core language
+enhancements.  Particularly prominent performance optimisations could go
+here, but most should go in the L</Performance Enhancements> section.
 
-On platforms that implement neither the C99 standard nor the POSIX 2001
-standard, determining if the current locale is UTF8 or not depends on
-heuristics.  These are improved in this release.
+[ List each enhancement as a =head2 entry ]
 
 =head1 Security
 
-=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available
+XXX Any security-related notices go here.  In particular, any security
+vulnerabilities closed should be noted here rather than in the
+L</Selected Bug Fixes> section.
+
+[ List each security issue as a =head2 entry ]
 
-The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
-gcc 4.*, is now always used for compiling Perl, if available.
+=head1 Incompatible Changes
 
-Note that this isn't necessarily a huge step since in many platforms
-the step had already been taken several years ago: many Linux
-distributions (like Fedora) have been using this option for Perl,
-and OS X has enforced the same for many years.
+XXX For a release on a stable branch, this section aspires to be:
 
+    There are no changes intentionally incompatible with 5.XXX.XXX
+    If any exist, they are bugs, and we request that you submit a
+    report.  See L</Reporting Bugs> below.
+
+[ List each incompatible change as a =head2 entry ]
 
 =head1 Deprecations
 
-=head2 C<< /\C/ >> character class
+XXX Any deprecated features, syntax, modules etc. should be listed here.
 
-This character class, which matches a single byte, even if it appears
-in a multi-byte character has been deprecated. Matching single bytes
-in a multi-byte character breaks encapsulation, and can corrupt utf8
-strings.
+=head2 Module removals
 
-=head1 Performance Enhancements
+XXX Remove this section if inapplicable.
 
-=over 4
+The following modules will be removed from the core distribution in a
+future release, and will at that time need to be installed from CPAN.
+Distributions on CPAN which require these modules will need to list them as
+prerequisites.
 
-=item *
+The core versions of these modules will now issue C<"deprecated">-category
+warnings to alert you to this fact.  To silence these deprecation warnings,
+install the modules in question from CPAN.
 
-Refactoring of C<< pp_tied >> and CC<< pp_ref >> for small improvements.
+Note that these are (with rare exceptions) fine modules that you are encouraged
+to continue to use.  Their disinclusion from core primarily hinges on their
+necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
+not usually on concerns over their design.
 
-=item *
+=over
 
-Pathtools don't try to load XS on miniperl.
+=item XXX
 
-=item *
+XXX Note that deprecated modules should be listed here even if they are listed
+as an updated module in the L</Modules and Pragmata> section.
 
-A typo fix reduces the size of the C<< OP >> structure.
+=back
+
+[ List each other deprecation as a =head2 entry ]
+
+=head1 Performance Enhancements
+
+XXX Changes which enhance performance without changing behaviour go here.
+There may well be none in a stable release.
+
+[ List each enhancement as a =item entry ]
+
+=over 4
 
 =item *
 
-Hash lookups where the key is a constant is faster.
+XXX
 
 =back
 
 =head1 Modules and Pragmata
 
-=head2 Updated Modules and Pragmata
+XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
+go here.  If Module::CoreList is updated, generate an initial draft of the
+following sections using F<Porting/corelist-perldelta.pl>.  A paragraph summary
+for important changes should then be added by hand.  In an ideal world,
+dual-life modules would have a F<Changes> file that could be cribbed.
 
-=over 4
+[ Within each section, list entries as a =item entry ]
 
-=item *
+=head2 New Modules and Pragmata
 
-L<arybase> has been upgraded from version 0.07 to 0.08.
+=over 4
 
 =item *
 
-L<B> has been upgraded from version 1.49 to 1.50.
+XXX
 
-=item *
+=back
+
+=head2 Updated Modules and Pragmata
 
-L<Devel::Peek> has been upgraded from version 1.17 to 1.18.
+=over 4
 
 =item *
 
-L<experimental> has been upgraded from version 0.007 to 0.008.
+L<XXX> has been upgraded from version A.xx to B.yy.
 
-=item *
+=back
 
-L<ExtUtils::Manifest> has been upgraded from version 1.63 to 1.64.
+=head2 Removed Modules and Pragmata
+
+=over 4
 
 =item *
 
-L<File::Copy> has been upgraded from version 2.29 to 2.30.
+XXX
 
-=item *
+=back
 
-The PathTools module collection (L<File::Spec> and friends) has been
-upgraded from version 3.48 to 3.49.
+=head1 Documentation
 
-=item *
+XXX Changes to files in F<pod/> go here.  Consider grouping entries by
+file and be sure to link to the appropriate page, e.g. L<perlfunc>.
 
-L<Filter::Simple> has been upgraded from version 0.91 to 0.92.
+=head2 New Documentation
 
-=item *
+XXX Changes which create B<new> files in F<pod/> go here.
 
-L<Hash::Util> has been upgraded from version 0.17 to 0.18.
+=head3 L<XXX>
 
-=item *
+XXX Description of the purpose of the new file here
 
-L<IO> has been upgraded from version 1.32 to 1.33.
+=head2 Changes to Existing Documentation
 
-=item *
+XXX Changes which significantly change existing files in F<pod/> go here.
+However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
+section.
 
-L<IO::Socket::IP> has been upgraded from version 0.29 to 0.31.
+=head3 L<XXX>
 
-A better fix for subclassing C<connect()>.
-L<[cpan #95983]|https://rt.cpan.org/Ticket/Display.html?id=95983>
-L<[cpan #97050]|https://rt.cpan.org/Ticket/Display.html?id=97050>
+=over 4
 
 =item *
 
-L<IPC::Open3> has been upgraded from version 1.16 to 1.17.
+XXX Description of the change here
 
-=item *
+=back
 
-L<Math::BigInt> has been upgraded from version 1.9995 to 1.9996.
+=head1 Diagnostics
 
-Correct handling of subclasses.
-L<[cpan #96254]|https://rt.cpan.org/Ticket/Display.html?id=96254>
-L<[cpan #96329]|https://rt.cpan.org/Ticket/Display.html?id=96329>
+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>.
 
-=item *
+XXX New or changed warnings emitted by the core's C<C> code go here.  Also
+include any changes in L<perldiag> that reconcile it to the C<C> code.
 
-L<Module::CoreList> has been upgraded from version 5.021001_01 to 5.021002.
+=head2 New Diagnostics
 
-=item *
+XXX Newly added diagnostic messages go under here, separated into New Errors
+and New Warnings
+
+=head3 New Errors
 
-L<Pod::Usage> has been upgraded from version 1.63 to 1.64.
+=over 4
 
 =item *
 
-L<POSIX> has been upgraded from version 1.40 to 1.41.
+XXX L<message|perldiag/"message">
 
-=item *
+=back
 
-L<threads> has been upgraded from version 1.94 to 1.95.
+=head3 New Warnings
+
+=over 4
 
 =item *
 
-L<warnings> has been upgraded from version 1.24 to 1.26.
+XXX L<message|perldiag/"message">
 
 =back
 
-=head1 Documentation
+=head2 Changes to Existing Diagnostics
 
-=head2 Changes to Existing Documentation
-
-=head3 L<< perlpolicy >>
+XXX Changes (i.e. rewording) of diagnostic messages go here
 
 =over 4
 
 =item *
 
-We now have a code of conduct for the I<< p5p >> mailing list, as documented
-in L<< perlpolicy/STANDARDS OF CONDUCT >>.
+XXX Describe change here
 
 =back
 
-=head3 L<< perlfunc >>
+=head1 Utility Changes
+
+XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
+Most of these are built within the directory F<utils>.
+
+[ List utility changes as a =head2 entry for each utility and =item
+entries for each change
+Use L<XXX> with program names to get proper documentation linking. ]
+
+=head2 L<XXX>
 
 =over 4
 
 =item *
 
-Improve documentation of C<< our >>.
+XXX
 
 =back
 
-=head3 L<< perlsyn >>
+=head1 Configuration and Compilation
+
+XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
+go here.  Any other changes to the Perl build process should be listed here.
+However, any platform-specific changes should be listed in the
+L</Platform Support> section, instead.
+
+[ List changes as a =item entry ].
 
 =over 4
 
 =item *
 
-The empty conditional in C<< for >> and C<< while >> is now documented
-in L<< perlsyn >>.
+XXX
 
 =back
 
-=head1 Diagnostics
+=head1 Testing
 
-=head2 New Diagnostics
+XXX Any significant changes to the testing of a freshly built perl should be
+listed here.  Changes which create B<new> files in F<t/> go here as do any
+large changes to the testing harness (e.g. when parallel testing was added).
+Changes to existing files in F<t/> aren't worth summarizing, although the bugs
+that they represent may be covered elsewhere.
 
-=head3 New Warnings
+[ List each test improvement as a =item entry ]
 
 =over 4
 
 =item *
 
-L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
-as 0 in increment (++)">
+XXX
 
-(W numeric) The indicated string was fed as an argument to the C<++> operator
-which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
-See L<perlop/Auto-increment and Auto-decrement> for details.
-
-=item *
+=back
 
-L<Redundant argument in %s|perldiag/Redundant argument in %s>
+=head1 Platform Support
 
-(W redundant) You called a function with more arguments than other
-arguments you supplied indicated would be needed. Currently only
-emitted when a printf-type format required fewer arguments than were
-supplied, but might be used in the future for e.g. L<perlfunc/pack>.
+XXX Any changes to platform support should be listed in the sections below.
 
-The warnings category C<< redundant >> is new. See also [RT #121025]
+[ Within the sections, list each platform as a =item entry with specific
+changes as paragraphs below it. ]
 
-=back
+=head2 New Platforms
 
-=head1 Configuration and Compilation
+XXX List any platforms that this version of perl compiles on, that previous
+versions did not.  These will either be enabled by new files in the F<hints/>
+directories, or new subdirectories and F<README> files at the top level of the
+source tree.
 
 =over 4
 
-=item *
+=item XXX-some-platform
 
-A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
-see the discussion below at L<< /Internal Changes >>.
+XXX
 
 =back
 
-=head1 Testing
+=head2 Discontinued Platforms
+
+XXX List any platforms that this version of perl no longer compiles on.
 
 =over 4
 
-=item *
+=item XXX-some-platform
 
-C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
-more compatible with C<< Test::More >>.
+XXX
 
 =back
 
-=head1 Platform Support
-
 =head2 Platform-Specific Notes
 
+XXX List any changes for specific platforms.  This could include configuration
+and compilation changes or changes in portability/compatibility.  However,
+changes within modules for platforms should generally be listed in the
+L</Modules and Pragmata> section.
+
 =over 4
 
-=item Solaris
+=item XXX-some-platform
 
-Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
-didn't follow implied dependencies to build C<perldtrace.h>.  Added an
-explicit dependency to C<depend>.
-L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>
+XXX
 
 =back
 
 =head1 Internal Changes
 
-=over 4
-
-=item *
+XXX Changes which affect the interface available to C<XS> code go here.  Other
+significant internal changes for future core maintainers should be noted as
+well.
 
-The following private API functions had their context parameter removed,
-C<Perl_cast_ulong>,  C<Perl_cast_i32>, C<Perl_cast_iv>,    C<Perl_cast_uv>,
-C<Perl_cv_const_sv>, C<Perl_mg_find>,  C<Perl_mg_findext>, C<Perl_mg_magical>,
-C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
+[ List each change as a =item entry ]
 
-Users of the public API prefix-less calls remain unaffected.
+=over 4
 
 =item *
 
-Experimental support for ops in the optree to be able to locate their
-parent, if any. A general-purpose function, C<< op_sibling_splice() >>
-allows for general manipulating an C<< op_sibling >> chain. The last op
-in such a chain is now marked with the field C<< op_lastsib >>.
-
-A new build define, C<< -DPERL_OP_PARENT >> has been added; if
-given, it forces the core to use C<< op_lastsib >> to detect the
-last sibling in a chain, freeing the last C<< op_sibling >> pointer,
-which then points back to the parent (instead of being C<< NULL >>).
-
-A C-level C<< op_parent() >> function, and a C<< B >> C<< parent() >> method
-have been added; under a default build, they return C<< NULL >>, but when
-C<< -DPERL_OP_PARENT >> has been set, they return the parent of the current op.
+XXX
 
 =back
 
 =head1 Selected Bug Fixes
 
+XXX Important bug fixes in the core language are summarized here.  Bug fixes in
+files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
+
+[ List each fix as a =item entry ]
+
 =over 4
 
 =item *
 
-C<< s///e >> on tainted utf8 strings got C<< pos() >> messed up. This bug,
-introduced in 5.20, is now fixed. [RT #122148]
+XXX
 
-=item *
+=back
+
+=head1 Known Problems
+
+XXX Descriptions of platform agnostic bugs we know we can't fix go here.  Any
+tests that had to be C<TODO>ed for the release would be noted here.  Unfixed
+platform specific bugs also go here.
 
-A non-word boundary in a regular expression (C<< \B >>) did not always
-match the end of the string; in particular C<< q{} =~ /\B/ >> did not
-match. This bug, introduced in perl 5.14, is now fixed. [RT #122090]
+[ List each fix as a =item entry ]
+
+=over 4
 
 =item *
 
-C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
-[RT #122171].
+XXX
 
 =back
 
-=head1 Acknowledgements
+=head1 Errata From Previous Releases
 
-Perl 5.21.2 represents approximately 4 weeks of development since Perl 5.21.1
-and contains approximately 11,000 lines of changes across 220 files from 27
-authors.
+=over 4
+
+=item *
 
-Excluding auto-generated files, documentation and release tools, there were
-approximately 5,700 lines of changes to 140 .pm, .t, .c and .h files.
+XXX Add anything here that we forgot to add, or were mistaken about, in
+the perldelta of a previous release.
 
-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 5.21.2:
+=back
+
+=head1 Obituary
 
-Aaron Crane, Abhijit Menon-Sen, Abigail, Alexandr Ciornii, brian d foy, Brian
-Fraser, Chris 'BinGOs' Williams, Craig A. Berry, Daniel Dragan, David Golden,
-David Mitchell, Dmitri Tikhonov, George Greer, H.Merijn Brand, James E Keenan,
-Jarkko Hietaniemi, Karen Etheridge, Karl Williamson, Matthew Horsfall, Peter
-John Acklam, Peter Martini, Reini Urban, Ricardo Signes, Steve Hay, Tony Cook,
-Yves Orton, Ævar Arnfjörð Bjarmason.
+XXX If any significant core contributor has died, we've added a short obituary
+here.
 
-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.
+=head1 Acknowledgements
 
-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.
+XXX Generate this with:
 
-For a more complete list of all of Perl's historical contributors, please see
-the F<AUTHORS> file in the Perl source distribution.
+  perl Porting/acknowledgements.pl v5.21.2..HEAD
 
 =head1 Reporting Bugs
 
diff --git a/vms/descrip_mms.template b/vms/descrip_mms.template
index 6ec85c011b..514945866f 100644
--- a/vms/descrip_mms.template
+++ b/vms/descrip_mms.template
@@ -307,7 +307,7 @@ utils : $(utils1) $(utils2) $(utils3) $(utils4) $(utils5)
 extra.pods : miniperl
 	@ @extra_pods.com
 
-PERLDELTA_CURRENT = [.pod]perl5212delta.pod
+PERLDELTA_CURRENT = [.pod]perl5213delta.pod
 
 $(PERLDELTA_CURRENT) : [.pod]perldelta.pod
 	Copy/NoConfirm/Log $(MMS$SOURCE) $(PERLDELTA_CURRENT)
diff --git a/win32/Makefile b/win32/Makefile
index 3b0c701fb4..c821ca832b 100644
--- a/win32/Makefile
+++ b/win32/Makefile
@@ -1155,7 +1155,7 @@ utils: $(PERLEXE) ..\utils\Makefile
 	copy ..\README.tw       ..\pod\perltw.pod
 	copy ..\README.vos      ..\pod\perlvos.pod
 	copy ..\README.win32    ..\pod\perlwin32.pod
-	copy ..\pod\perldelta.pod ..\pod\perl5212delta.pod
+	copy ..\pod\perldelta.pod ..\pod\perl5213delta.pod
 	cd ..\win32
 	$(PERLEXE) $(PL2BAT) $(UTILS)
 	$(MINIPERL) -I..\lib ..\autodoc.pl ..
@@ -1250,7 +1250,7 @@ distclean: realclean
 	-if exist $(LIBDIR)\Win32API rmdir /s /q $(LIBDIR)\Win32API
 	-if exist $(LIBDIR)\XS rmdir /s /q $(LIBDIR)\XS
 	-cd $(PODDIR) && del /f *.html *.bat roffitall \
-	    perl5212delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
+	    perl5213delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
 	    perlapi.pod perlbs2000.pod perlce.pod perlcn.pod perlcygwin.pod \
 	    perldos.pod perlfreebsd.pod perlhaiku.pod perlhpux.pod \
 	    perlhurd.pod perlintern.pod perlirix.pod perljp.pod perlko.pod \
diff --git a/win32/makefile.mk b/win32/makefile.mk
index d376a8cff6..936174855d 100644
--- a/win32/makefile.mk
+++ b/win32/makefile.mk
@@ -1349,7 +1349,7 @@ utils: $(PERLEXE) ..\utils\Makefile
 	copy ..\README.tw       ..\pod\perltw.pod
 	copy ..\README.vos      ..\pod\perlvos.pod
 	copy ..\README.win32    ..\pod\perlwin32.pod
-	copy ..\pod\perldelta.pod ..\pod\perl5212delta.pod
+	copy ..\pod\perldelta.pod ..\pod\perl5213delta.pod
 	$(PERLEXE) $(PL2BAT) $(UTILS)
 	$(MINIPERL) -I..\lib ..\autodoc.pl ..
 	$(MINIPERL) -I..\lib ..\pod\perlmodlib.PL -q ..
@@ -1443,7 +1443,7 @@ distclean: realclean
 	-if exist $(LIBDIR)\Win32API rmdir /s /q $(LIBDIR)\Win32API
 	-if exist $(LIBDIR)\XS rmdir /s /q $(LIBDIR)\XS
 	-cd $(PODDIR) && del /f *.html *.bat roffitall \
-	    perl5212delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
+	    perl5213delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
 	    perlapi.pod perlbs2000.pod perlce.pod perlcn.pod perlcygwin.pod \
 	    perldos.pod perlfreebsd.pod perlhaiku.pod perlhpux.pod \
 	    perlhurd.pod perlintern.pod perlirix.pod perljp.pod perlko.pod \
diff --git a/win32/pod.mak b/win32/pod.mak
index ed33b2e1c0..810a5f7256 100644
--- a/win32/pod.mak
+++ b/win32/pod.mak
@@ -39,6 +39,7 @@ POD = perl.pod	\
 	perl5210delta.pod	\
 	perl5211delta.pod	\
 	perl5212delta.pod	\
+	perl5213delta.pod	\
 	perl561delta.pod	\
 	perl56delta.pod	\
 	perl581delta.pod	\
@@ -171,6 +172,7 @@ MAN = perl.man	\
 	perl5210delta.man	\
 	perl5211delta.man	\
 	perl5212delta.man	\
+	perl5213delta.man	\
 	perl561delta.man	\
 	perl56delta.man	\
 	perl581delta.man	\
@@ -303,6 +305,7 @@ HTML = perl.html	\
 	perl5210delta.html	\
 	perl5211delta.html	\
 	perl5212delta.html	\
+	perl5213delta.html	\
 	perl561delta.html	\
 	perl56delta.html	\
 	perl581delta.html	\
@@ -435,6 +438,7 @@ TEX = perl.tex	\
 	perl5210delta.tex	\
 	perl5211delta.tex	\
 	perl5212delta.tex	\
+	perl5213delta.tex	\
 	perl561delta.tex	\
 	perl56delta.tex	\
 	perl581delta.tex	\