There are several advantages to this:
-=over
+=over
=item *
new kinds of keyword-headed expression and compound statement. The
syntax following the keyword is defined entirely by the extension. This
allow a completely non-Perl sublanguage to be parsed inline, with the
-correct ops cleanly generated.
+correct ops cleanly generated.
See L<perlapi/PL_keyword_plugin> for the mechanism. The Perl core
source distribution also includes a new module
=head2 Deprecations warn by default
-Perl now defaults to issuing a warning if a deprecated language feature
-is used.
+Over the years, Perl's developers have deprecated a number of language
+features for a variety of reasons. Perl now defaults to issuing a
+warning if a deprecated language feature is used. Many of the deprecations
+Perl now warns you about have been deprecated for many years. You can
+find a list of what was deprecated in a given release of Perl in the
+C<perl5xxdelta.pod> file for that release.
To disable this feature in a given lexical scope, you should use C<no
warnings 'deprecated';> For information about which language features
C<site_perl> and C<vendor_perl> will now be loaded in preference to
those installed in C<ARCHLIB> and C<PRIVLIB>.
+
+=head2 REGEXPs are now first class
+
+Internally, Perl now treates compiled regular expressions (such as
+those created with C<qr//>) as first class entities. Perl modules which
+serialize, deserialize or otherwise have deep interaction with Perl's
+internal data structures need to be updated for this change. Affected
+modules include L<FreezeThaw>,L<Data::Dump::Streamer> and L<Regexp::Copy>.
+
+
=head2 Switch statement changes
The C<given>/C<when> switch statement handles complex statements better
To better match all other flow control statements, C<foreach> may no
longer be used as an attribute.
+=item *
+
+Perl's command-line switch "-P", which was deprecated in version 5.10.0, has
+now been removed.
+
=back
a later release where the system administrator needs to know to install
multiple packages to get that same functionality.
+You can silence these deprecation warnings by installing the modules
+in question from CPAN. To install the latest version of all of them,
+just install C<Task::Deprecations::5_12>.
+
=over
=item L<Class::ISA>
=item *
-REGEXPs are now first class.
-
-=item *
-
C<Perl_vcroak()> now accepts a null first argument. In addition, a full
audit was made of the "not NULL" compiler annotations, and those for
several other internal functions were corrected.
This uses a new warnings category: "imprecision".
-=item *
+=item *
C<lc>, C<uc>, C<lcfirst>, and C<ucfirst> warn when passed undef.
=item *
F<h2xs> no longer incorrectly treats enum values like macros.
-It also now handles C++ style comments (C<//>) properly in enums.
+It also now handles C++ style comments (C<//>) properly in enums.
=item *
The F<Artistic> and F<Copying> files for copyright information.
+L<http://dev.perl.org/perl5/errata.html> for a list of issues
+found after this release, as well as a list of CPAN modules known
+to be incompatible with this release.
+
=cut