=head1 NAME
-perldelta - what is new for perl v5.9.3
+perl593delta - what is new for perl v5.9.3
=head1 DESCRIPTION
=head2 Parsing of C<-f _>
-C<_> is now forced to be a bareword after a filetest operator. This solves
-a number of misparsing issues when a global C<_> subroutine is defined.
+The identifier C<_> is now forced to be a bareword after a filetest
+operator. This solves a number of misparsing issues when a global C<_>
+subroutine is defined.
=head2 C<mkdir()>
=head2 The C<feature> pragma
The C<feature> pragma is used to enable new syntax that would break Perl's
-backward-compatibility with older releases of the language. It's a lexical
+backwards-compatibility with older releases of the language. It's a lexical
pragma, like C<strict> or C<warnings>.
Currently the following new features are available: C<switch> (adds a
Those features are described below.
Note that C<err> low-precedence defined-or operator used to be enabled by
-default, but as a weak keyword. It's now only recognized when explicitly
-turned on.
+default (although as a weak keyword, meaning that any function would
+override it). It's now only recognized when explicitly turned on (and is
+then a regular keyword).
+
+Those features, and the C<feature> pragma itself, have been contributed by
+Robin Houston.
=head2 Switch and Smart Match operator
-XXX
+Perl 5 now has a switch statement. It's available when C<use feature
+'switch'> is in effect. This feature introduces three new keywords,
+C<given>, C<when>, and C<default>:
+
+ given ($foo) {
+ when (/^abc/) { $abc = 1; }
+ when (/^def/) { $def = 1; }
+ when (/^xyz/) { $xyz = 1; }
+ default { $nothing = 1; }
+ }
+
+A more complete description of how Perl matches the switch variable
+against the C<when> conditions is given in L<perlsyn/"Switch statements">.
+
+This kind of match is called I<smart match>, and it's also possible to use
+it outside of switch statements, via the new C<~~> operator (enabled via
+the C<use feature '~~'> directive). See L<perlsyn/"Smart matching in
+detail">.
=head2 C<say()>
-say() is a new built-in, only avaiable when C<use feature 'say'> is in
+say() is a new built-in, only available when C<use feature 'say'> is in
effect, that is similar to print(), but that implicitly appends a newline
to the printed string. See L<perlfunc/say>.
C<CLONE>, C<CLONE_SKIP> is called once per package; however, it is called
just before cloning starts, and in the context of the parent thread. If it
returns a true value, then no objects of that class will be cloned. See
-L<perlmod> for details.
+L<perlmod> for details. (Contributed by Dave Mitchell.)
=head2 C<${^CHILD_ERROR_NATIVE}>
A new internal variable, C<${^CHILD_ERROR_NATIVE}>, gives the native
status returned by the last pipe close, backtick command, successful call
to wait() or waitpid(), or from the system() operator. See L<perlrun> for
-details.
+details. (Contributed by Gisle Aas.)
=head2 Assertions
The support for assertions, introduced in perl 5.9.0, has been improved.
The syntax for the C<-A> command-line switch has changed; it now accepts
an optional module name, defaulting to C<assertions::activate>. See
-L<assertions> and L<perlrun>.
+L<assertions> and L<perlrun>. (Contributed by Salvador Fandiño García.)
=head2 Unicode Character Database 4.1.0
=head2 C<no VERSION>
You can now use C<no> followed by a version number to specify that you
-want to use a version of perl inferior to the specified one.
+want to use a version of perl older than the specified one.
=head2 Recursive sort subs
-You can now use recursive subroutines with sort().
+You can now use recursive subroutines with sort(), thanks to Robin Houston.
=head2 Effect of pragmas in eval
=head2 New B<-E> command-line switch
B<-E> is equivalent to B<-e>, but it implicitly enables all
-optional features.
+optional features (like C<use feature ":5.10">).
+
+=head2 C<chdir>, C<chmod> and C<chown> on filehandles
+
+C<chdir>, C<chmod> and C<chown> can now work on filehandles as well as
+filenames, if the system supports respectively C<fchdir>, C<fchmod> and
+C<fchown>, thanks to a patch provided by Gisle Aas.
+
+=head2 OS groups
+
+C<$(> and C<$)> now return groups in the order where the OS returns them,
+thanks to Gisle Aas. This wasn't previously the case.
=head1 Modules and Pragmata
-=head2 C<feature>
+=head2 New Core Modules
+
+=over 4
+
+=item *
+
+A new pragma, C<feature>, has been added; see above in L</"Core
+Enhancements">.
+
+=item *
+
+C<assertions::compat>, also available on CPAN, allows the use of assertions on
+perl versions prior to 5.9.0 (that is the first one to natively support
+them).
+
+=item *
+
+C<Math::BigInt::FastCalc> is an XS-enabled, and thus faster, version of
+C<Math::BigInt::Calc>.
-This new module implements the C<feature> pragma; see above in
-L</"Core Enhancements">.
+=item *
+
+C<Compress::Zlib> is an interface to the zlib compression library. It
+comes with a bundled version of zlib, so having a working zlib is not a
+prerequisite to install it. It's used by C<Archive::Tar> (see below).
+
+=item *
+
+C<IO::Zlib> is an C<IO::>-style interface to C<Compress::Zlib>.
-=head2 C<assertions::compat>
+=item *
-=head2 C<Math::BigInt::FastCalc>
+C<Archive::Tar> is a module to manipulate C<tar> archives.
-=head2 C<Compress::Zlib>
+=item *
-=head2 C<IO::Zlib>
+C<Digest::SHA> is a module used to calculate many types of SHA digests,
+has been included for SHA support in the CPAN module.
-=head2 C<Archive::Tar>
+=item *
+
+C<ExtUtils::CBuilder> and C<ExtUtils::ParseXS> have been added.
+
+=back
=head1 Utility Changes
=head2 C<ptar>
+C<ptar> is a pure perl implementation of C<tar>, that comes with
+C<Archive::Tar>.
+
+=head2 C<ptardiff>
+
+C<ptardiff> is a small script used to generate a diff between the contents
+of a tar archive and a directory tree. Like C<ptar>, it comes with
+C<Archive::Tar>.
+
+=head2 C<shasum>
+
+This command-line utility, used to print or to check SHA digests, comes
+with the new C<Digest::SHA> module.
+
+=head2 C<h2xs> enhancements
+
+C<h2xs> implements a new option C<--use-xsloader> to force use of
+C<XSLoader> even in backwards compatible modules.
+
+The handling of authors' names that had apostrophes has been fixed.
+
+Any enums with negative values are now skipped.
+
+=head2 C<perlivp> enhancements
+
+C<perlivp> no longer checks for F<*.ph> files by default. Use the new C<-a>
+option to run I<all> tests.
+
=head1 Documentation
=head2 Perl Glossary
The L<perlglossary> manpage is a glossary of terms used in the Perl
-documentation, technical and otherwise.
+documentation, technical and otherwise, kindly provided by O'Reilly Media,
+Inc.
+
+L<perltodo> now lists a rough roadmap to Perl 5.10.
=head1 Performance Enhancements
Some pure-perl code that perl was using to retrieve Unicode properties and
transliteration mappings has been reimplemented in XS.
-=head2 Constants subroutines
+=head2 Constant subroutines
+
+The interpreter internals now support a far more memory efficient form of
+inlineable constants. Storing a reference to a constant value in a symbol
+table is equivalent to a full typeglob referencing a constant subroutine,
+but using about 400 bytes less memory. This proxy constant subroutine is
+automatically upgraded to a real typeglob with subroutine if necessary.
+The approach taken is analogous to the existing space optimisation for
+subroutine stub declarations, which are stored as plain scalars in place
+of the full typeglob.
+
+Several of the core modules have been converted to use this feature for
+their system dependent constants - as a result C<use POSIX;> now takes about
+200K less memory.
+
+=head2 C<PERL_DONT_CREATE_GVSV>
+
+The new compilation flag C<PERL_DONT_CREATE_GVSV>, introduced as an option
+in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl
+from creating an empty scalar with every new typeglob. See L<perl589delta>
+for details.
+
+=head2 Weak references are cheaper
+
+Weak reference creation is now I<O(1)> rather than I<O(n)>, courtesy of
+Nicholas Clark. Weak reference deletion remains I<O(n)>, but if deletion only
+happens at program exit, it may be skipped completely.
-XXX
+=head2 sort() enhancements
+
+Salvador Fandiño provided improvements to reduce the memory usage of C<sort>
+and to speed up some cases.
=head1 Installation and Configuration Improvements
+=head2 Compilation improvements
+
+Parallel makes should work properly now, although there may still be problems
+if C<make test> is instructed to run in parallel.
+
+Building with Borland's compilers on Win32 should work more smoothly. In
+particular Steve Hay has worked to side step many warnings emitted by their
+compilers and at least one C compiler internal error.
+
+Perl extensions on Windows now can be statically built into the Perl DLL,
+thanks to a work by Vadim Konovalov.
+
=head2 New Or Improved Platforms
Perl is being ported to Symbian OS. See L<perlsymbian> for more
=head2 New probes
-Perl will detect and use internally futimes(2) if available.
+C<Configure> will now detect C<clearenv> and C<unsetenv>, thanks to a
+patch from Alan Burlison. It will also probe for C<futimes> (and use it
+internally if available), and whether C<sprintf> correctly returns the
+length of the formatted string.
=head2 Module auxiliary files
=head2 Calling CORE::require()
CORE::require() and CORE::do() were always parsed as require() and do()
-when they were overriden. This is now fixed.
+when they were overridden. This is now fixed.
=head2 Subscripts of slices
Using the sprintf() function with some formats could lead to a buffer
overflow in some specific cases. This has been fixed, along with several
-other bugs, notably in bound checking.
+other bugs, notably in bounds checking.
-In related fixes, a format string injection vulnerability has been fixed
-in Sys::Syslog.
+In related fixes, it was possible for badly written code that did not follow
+the documentation of C<Sys::Syslog> to have formatting vulnerabilities.
+C<Sys::Syslog> has been changed to protect people from poor quality third
+party code.
+
+=head2 no warnings 'category' works correctly with -w
+
+Previously when running with warnings enabled globally via C<-w>, selective
+disabling of specific warning categories would actually turn off all warnings.
+This is now fixed; now C<no warnings 'io';> will only turn off warnings in the
+C<io> class. Previously it would erroneously turn off all warnings.
=head2 Smaller fixes
=item *
+Trailing spaces are now trimmed from C<$!> and C<$^E>.
+
+=item *
+
+Operations that require perl to read a process's list of groups, such as reads
+of C<$(> and C<$)>, now dynamically allocate memory rather than using a
+fixed sized array. The fixed size array could cause C stack exhaustion on
+systems configured to use large numbers of groups.
+
+=item *
+
C<PerlIO::scalar> now works better with non-default C<$/> settings.
=item *
-You can now use the C<x> operator to repeat a C<qw//> list. This used
-to raise a syntax error. For example: C<qw(foo bar) x 3>.
+The C<x> repetition operator is now able to operate on C<qw//> lists. This
+used to raise a syntax error.
=item *
=item *
-C<//g> matches used to loop infinitely on tainted data.
+Perl will now use the C library calls C<unsetenv> and C<clearenv> if present
+to delete keys from C<%ENV> and delete C<%ENV> entirely, thanks to a patch
+from Alan Burlison.
=back
character, unless when the C<bytes> pragma is in effect, where the low
eight bytes of the value are used.
+=item *
+
+Some case insensitive matches between UTF-8 encoded data and 8 bit regexps,
+and vice versa, could give malformed character warnings. These have been
+fixed by Dave Mitchell and Yves Orton.
+
+=item *
+
+C<lcfirst> and C<ucfirst> could corrupt the string for certain cases where
+the length UTF-8 encoding of the string in lower case, upper case or title
+case differed. This was fixed by Nicholas Clark.
+
=back
=head1 New or Changed Diagnostics
$r = do {my @a; \$#a};
$$r = 503;
+=head2 Non-string passed as bitmask
+
+This is a new warning, produced when number has been passed as a argument to
+select(), instead of a bitmask.
+
+ # Wrong, will now warn
+ $rin = fileno(STDIN);
+ ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
+
+ # Should be
+ $rin = '';
+ vec($rin,fileno(STDIN),1) = 1;
+ ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
+
=head2 Search pattern not terminated or ternary operator parsed as search pattern
This syntax error indicates that the lexer couldn't find the final
my $x; our $x; # warns
our $x; my $x; # warns
-On the other hand, the following :
+On the other hand, the following:
our $x; our $x;
=head1 Changed Internals
-XXX consting
+In general, the source code of perl has been refactored, tied up, and
+optimized in many places. Also, memory management and allocation has been
+improved in a couple of points.
+
+Andy Lester supplied many improvements to determine which function
+parameters and local variables could actually be declared C<const> to the C
+compiler. Steve Peters provided new C<*_set> macros and reworked the core to
+use these rather than assigning to macros in LVALUE context.
+
+Dave Mitchell improved the lexer debugging output under C<-DT>.
A new file, F<mathoms.c>, has been added. It contains functions that are
no longer used in the perl core, but that remain available for binary or
The C<AvFLAGS> macro has been removed.
+The C<av_*()> functions, used to manipulate arrays, no longer accept null
+C<AV*> parameters.
+
=head2 B:: modules inheritance changed
The inheritance hierarchy of C<B::> modules has changed; C<B::NV> now
inherits from C<B::SV> (it used to inherit from C<B::IV>).
-=head1 Known Problems
-
-=head2 Platform Specific Problems
-
=head1 Reporting Bugs
If you find what you think is a bug, you might check the articles
https://perl5.git.perl.org / perl5.git / blobdiff