[ List each enhancement as a =head2 entry ]
+=head2 faster array and hash lookups
+
+Array and hash lookups (especially nested ones) that use only constants
+or simple variables as keys, are now considerably faster. See
+L</Internal Changes> for more details.
+
=head2 C<fileno> now works on directory handles
When the relevant support is available in the operating system, the
pragma is deprecated, but in the meantime, it could adversely affect
unrelated modules that are included in the same program.
+=head2 List slices returning empty lists
+
+List slices return an empty list now only if the original list was empty
+(or if there are no indices). Formerly, a list slice would return an empty
+list if all indices fell outside the original list. [perl #114498]
+
=head1 Deprecations
XXX Any deprecated features, syntax, modules etc. should be listed here.
process of this version. This data is now memory mapped from disk and shared
between perl processes from the same perl binary.
+=item *
+
+If method and class names are known at compile time, hashes are precomputed
+to speed up run-time method lookup. Also, compound method names like
+C<SUPER::new> are parsed at compile time, to save having to parse them at
+run time.
+
=back
=head1 Modules and Pragmata
BEGIN blocks at the end of the enclosing scope are now deparsed in the
right place. [perl #77452]
+BEGIN blocks were sometimes deparsed as __ANON__, but are now always called
+BEGIN.
+
Lexical subroutines are now fully deparsed. [perl #116553]
+Deparsing of C<$lexical =~ //> was accidentally broken in 1.30 (perl
+5.21.6), omitting the C<$lexical =~>, but has now been fixed.
+
+C<Anything =~ y///r> with C</r> no longer omits the left-hand operand.
+
+The op trees that make up regexp code blocks are now deparsed for real.
+Formerly, the original string that made up the regular expression was used.
+That caused problems with C<qr/(?{<<heredoc})/> and multiline code blocks,
+which were deparsed incorrectly. [perl #123217] [perl #115256]
+
+C<$;> at the end of a statement no longer loses its semicolon.
+[perl #123357]
+
+Some cases of subroutine declarations stored in the stash in shorthand form
+were being omitted.
+
+Non-ASCII characters are now consistently escaped in strings, instead of
+some of the time. (There are still outstanding problems with regular
+expressions and identifiers that have not been fixed.)
+
+When prototype sub calls are deparsed with C<&> (e.g., under the B<-P>
+option), C<scalar> is now added where appropriate, to force the scalar
+context implied by the prototype.
+
+C<require(foo())>, C<do(foo())>, C<goto(foo())> and similar constructs with
+loop controls are now deparsed correctly. The outer parentheses are not
+optional.
+
+Whitespace is no longer escaped in regular expressions, because it was
+getting erroneously escaped within C<(?x:...)> sections.
+
+C<sub foo { foo() }> is now deparsed with those mandatory parentheses.
+
+C</@array/> is now deparsed as a regular expression, and not just
+C<@array>.
+
+C</@{-}/>, C</@{+}/> and C<$#{1}> are now deparsed with the braces, which
+are mandatory in these cases.
+
+In deparsing feature bundles, B::Deparse was emitting C<no feature;> first
+instead of C<no feature ':all';>. This has been fixed.
+
+C<chdir FH> is now deparsed without quotation marks.
+
+C<\my @a> is now deparsed without parentheses. (Parenthese would flatten
+the array.)
+
=item *
L<ExtUtils::ParseXS> has been upgraded from version 3.26 to 3.27.
Improve generated C<RETVAL> code generation to avoid repeated
references to C<ST(0)>. [perl #123278]
+Broaden and document the C</OBJ$/> to C</REF$/> typemap optimization
+for the C<DESTROY> method. [perl #123418]
+
=item *
The PathTools module collection has been upgraded from 3.52 to 3.53.
for two different internal representations of pad names has now been
removed.
+=item *
+
+The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros added in an earlier 5.21.x
+release have been renamed C<OpSIBLING> and C<OpHAS_SIBLING>, following the
+existing convention.
+
+=item *
+
+A new op class, C<UNOP_AUX>, has been added. This is a subclass of
+C<UNOP> with an C<op_aux> field added, which points to an array of unions
+of C<UV>, C<SV*> etc. It is intended for where an op needs to store more data
+than a simple C<op_sv> or whatever. Currently the only op of this type is
+C<OP_MULTIDEREF> (see below).
+
+=item *
+
+A new op has been added, C<OP_MULTIDEREF>, which performs one or more
+nested array and hash lookups where the key is a constant or simple
+variable. For example the expression C<$a[0]{$k}[$i]>, which previously
+involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
+by a single C<multideref> op. It can also handle C<local>, C<exists> and
+C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
+using C<aelem/helem>, and single-level array lookup with a small constant
+index is still done using C<aelemfast>.
+
=back
=head1 Selected Bug Fixes
On Win32, restoring in a child pseudo-process a variable that was
C<local()>ed in a parent pseudo-process before the C<fork> happened caused
memory corruption and a crash in the child pseudo-process (and therefore OS
-process).
+process). [perl #40565]
=item *
C<qr/@array(?{block})/> no longer dies with "Bizarre copy of ARRAY".
[#123344]
+=item *
+
+C<eval '$variable'> in nested named subroutines would sometimes look up a
+global variable even with a lexical variable in scope.
+
+In perl 5.20.0, C<sort CORE::fake> where 'fake' is anything other than a
+keyword started chopping of the last 6 characters and treating the result
+as a sort sub name. The previous behaviour of treating "CORE::fake" as a
+sort sub name has been restored. [perl #123410]
+
+=item *
+
+Outside of C<use utf8>, a single-character Latin-1 lexical variable is
+disallowed. The error message for it, "Can't use global $foo...", was
+giving garbage instead of the variable name.
+
=back
=head1 Known Problems
https://perl5.git.perl.org / perl5.git / blobdiff