=head1 NAME

perldelta - what is new for perl v5.9.3

=head1 DESCRIPTION

This document describes differences between the 5.9.2 and the 5.9.3
development releases. See L<perl590delta>, L<perl591delta> and
L<perl592delta> for the differences between 5.8.0 and 5.9.2.

=head1 Incompatible Changes

=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.

=head2 C<mkdir()>

C<mkdir()> without arguments now defaults to C<$_>.

=head2 Magic goto and eval

The construct C<eval { goto &foo }> is now disallowed. (Note that the
similar construct, but with C<eval("")> instead, was already forbidden.)

=head2 C<$#> has been removed

The deprecated C<$#> variable (output format for numbers) has been
removed. A new warning, C<$# is no longer supported>, has been added.

=head2 C<:unique>

The C<:unique> attribute has been made a no-op, since its current
implementation was fundamentally flawed and not threadsafe.

=head1 Core Enhancements

=head2 Switch and Smart Match operator

=head2 C<say()>

=head2 C<CLONE_SKIP()>

Perl has now support for the C<CLONE_SKIP> special subroutine. Like
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.

=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.

=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>.

=head2 Unicode Character Database 4.1.0

The copy of the Unicode Character Database included in Perl 5.9 has
been updated to 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.

=head1 Modules and Pragmata

=head2 C<feature>

=head2 C<assertions::compat>

=head2 C<Math::BigInt::FastCalc>

=head2 C<Compress::Zlib>

=head2 C<IO::Zlib>

=head2 C<Archive::Tar>

=head1 Utility Changes

=head2 C<ptar>

=head1 Documentation

=head2 Perl Glossary

The L<perlglossary> manpage is a glossary of terms used in the Perl
documentation, technical and otherwise.

=head1 Performance Enhancements

=head1 Installation and Configuration Improvements

=head2 New Or Improved Platforms

Perl is being ported to Symbian OS. See L<perlsymbian> for more
information.

=head2 Module auxiliary files

README files and changelogs for CPAN modules bundled with perl are no
longer installed.

=head1 Selected Bug Fixes

=head2 C<defined $$x>

C<use strict "refs"> was ignoring taking a hard reference in an argument
to defined(), as in :

    use strict "refs";
    my $x = "foo";
    if (defined $$x) {...}

This now correctly produces the run-time error C<Can't use string as a
SCALAR ref while "strict refs" in use>. (However, C<defined @$foo> and
C<defined %$foo> are still allowed. Those constructs are discouraged
anyway.)

=head2 Smaller fixes

=over 4

=item *

C<FindBin> now works better with directories where access rights are more
restrictive than usual.

=item *

Several memory leaks in ithreads were closed.

=item *

C<PerlIO::scalar> now works better with non-default C<$/> settings.

=item *

You can now use the C<x> operator to demultiply a C<qw//> list. This used
to raise a syntax error.

=back

=head2 More Unicode Fixes

=over 4

=item *

chr() on a negative value now gives C<\x{FFFD}>, the Unicode replacement
character, unless when the C<bytes> pragma is in effect, where the low
eight bytes of the value are used.

=back

=head1 New or Changed Diagnostics

=head2 Attempt to set length of freed array

This is a new warning, produced in situations like the following one:

    $r = do {my @a; \$#a};
    $$r = 503;

=head2 Search pattern not terminated or ternary operator parsed as search pattern

This syntax error indicates that the lexer couldn't find the final
delimiter of a C<?PATTERN?> construct. Mentioning the ternary operator in
this error message makes syntax diagnostic easier.

=head2 "%s" variable %s masks earlier declaration

This warning is now emitted in more consistent cases; in short, when one
of the declarations involved is a C<my> variable:

    my $x;   my $x;	# warns
    my $x;  our $x;	# warns
    our $x;  my $x;	# warns

On the other hand, the following :

    our $x; our $x;

now gives a C<"our" variable %s redeclared> warning.

=head1 Changed Internals

XXX consting

XXX mathoms

The C<AvFLAGS> macro has been removed.

=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
recently posted to the comp.lang.perl.misc newsgroup and the perl
bug database at http://bugs.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 B<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.

=head1 SEE ALSO

The F<Changes> file for 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