=head1 NAME
-perldelta - what's new for perl5.006 (as of 5.005_56)
+perldelta - what's new for perl v5.6 (as of v5.005_61)
=head1 DESCRIPTION
+This is an unsupported alpha release, meant for intrepid Perl developers
+only. The included sources may not even build correctly on some platforms.
+Subscribing to perl5-porters is the best way to monitor and contribute
+to the progress of development releases (see www.perl.org for info).
+
This document describes differences between the 5.005 release and this one.
=head1 Incompatible Changes
=head2 Perl Source Incompatibilities
-None known at this time.
+TODO
=head2 C Source Incompatibilities
=item C<PERL_POLLUTE>
Release 5.005 grandfathered old global symbol names by providing preprocessor
-macros for extension source compatibility. As of release 5.006, these
+macros for extension source compatibility. As of release 5.6, these
preprocessor definitions are not available by default. You need to explicitly
compile perl with C<-DPERL_POLLUTE> to get these definitions. For
extensions still using the old symbols, this option can be
perl Makefile.PL POLLUTE=1
+=item C<PERL_IMPLICIT_CONTEXT>
+
+This new build option provides a set of macros for all API functions
+such that an implicit interpreter/thread context argument is passed to
+every API function. As a result of this, something like C<sv_setsv(foo,bar)>
+amounts to a macro invocation that actually translates to something like
+C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
+to not have any significant source compatibility issues, the difference
+between a macro and a real function call will need to be considered.
+
+This means that there B<is> a source compatibility issue as a result of
+this if your extensions attempt to use pointers to any of the Perl API
+functions.
+
+Note that the above issue is not relevant to the default build of
+Perl, whose interfaces continue to match those of prior versions
+(but subject to the other options described here).
+
+PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
+with one of -Dusethreads, -Dusemultiplicity, or both.
+
+See L<perlguts/"The Perl API"> for detailed information on the
+ramifications of building Perl using this option.
+
=item C<PERL_POLLUTE_MALLOC>
Enabling Perl's malloc in release 5.005 and earlier caused
have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
EMBEDMYMALLOC preprocessor definitions.
-As of release 5.006, Perl's malloc family of functions have default names
+As of release 5.6, Perl's malloc family of functions have default names
distinct from the system versions. You need to explicitly compile perl with
C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
=head2 Binary Incompatibilities
-This release is not binary compatible with the 5.005 release or its
-maintenance versions.
+The default build of this release is binary compatible with the 5.005
+release or its maintenance versions.
+
+The usethreads or usemultiplicity builds are B<not> binary compatible
+with the corresponding builds in 5.005.
=head1 Core Changes
=head2 Lexically scoped warning categories
You can now control the granularity of warnings emitted by perl at a finer
-level using the C<use warning> pragma. See L<warning> for details.
+level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
+for details.
=head2 Binary numbers supported
=head2 64-bit support
-Better 64-bit support -- but full support still a distant goal. One
-must Configure with -Duse64bits to get Configure to probe for the
-extent of 64-bit support. Depending on the platform (hints file) more
-or less 64-awareness becomes available. As of 5.005_54 at least
-somewhat 64-bit aware platforms are HP-UX 11 or better, Solaris 2.6 or
-better, IRIX 6.2 or better. Naturally 64-bit platforms like Digital
-Unix and UNICOS also have 64-bit support.
+All platforms that have 64-bit integers either (a) natively as longs
+or ints (b) via special compiler flags (c) using long long are able to
+use "quads" (64-integers) as follows:
-=head2 Better syntax checks on parenthesized unary operators
+=over 4
-TODO
+=item constants in the code
-=head2 POSIX character class syntax [: :] supported
+=item arguments to oct() and hex()
-For example to match alphabetic characters use /[[:alpha:]]/.
-See L<perlre> for details.
+=item arguments to print(), printf() and sprintf()
+
+=item pack() and unpack() "q" format
+
+=item in basic arithmetics
+
+=item vec() (but see the below note about bit arithmetics)
+
+=back
+
+Note that unless you have the case (a) you will have to configure
+and compile Perl using the -Duse64bits Configure flag.
+
+Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) are not 64-bit clean.
+
+Last but not least: note that due to Perl's habit of always using
+floating point numbers the quads are still not true integers.
+When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
+-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
+are silently promoted to floating point numbers, after which they will
+start losing precision (their lower digits).
+
+=head2 Large file support
+
+If you have filesystems that support "large files" (files larger than
+2 gigabytes), you may now also be able to create and access them from Perl.
+
+Note that in addition to requiring a proper file system to do this you
+may also need to adjust your per-process (or even your per-system)
+maximum filesize limits before running Perl scripts that try to handle
+large files, especially if you intend to write such files.
+
+Adjusting your file system/system limits is outside the scope of Perl.
+For process limits, you may try to increase the limits using your
+shell's limit/ulimit command before running Perl. The BSD::Resource
+extension (not included with the standard Perl distribution) may also
+be of use.
+
+(Large file support is also related to 64-bit support, for obvious reasons)
+
+=head2 Better syntax checks on parenthesized unary operators
Expressions such as:
remains unchanged. See L<perlop>.
+=head2 POSIX character class syntax [: :] supported
+
+For example to match alphabetic characters use /[[:alpha:]]/.
+See L<perlre> for details.
+
=head2 Improved C<qw//> operator
The C<qw//> operator is now evaluated at compile time into a true list
The new format type modifier '!' is useful for packing and unpacking
native shorts, ints, and longs. See L<perlfunc/"pack">.
+=head2 pack() and unpack() support counted strings
+
+The template character '#' can be used to specify a counted string
+type to be packed or unpacked. See L<perlfunc/"pack">.
+
=head2 $^X variables may now have names longer than one character
Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
buffering mishaps suffered by users unaware of how Perl internally
handles I/O.
+=head2 Better diagnostics on meaningless filehandle operations
+
+Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
+are compile time errors. Attempting to read from filehandles that
+were opened only for writing will now produce warnings (just as
+writing to read-only filehandles does).
+
+=head2 Buffered data discarded from input filehandle when dup'ed.
+
+C<open(NEW, "E<lt>&OLD")> now discards any data that was previously
+read and buffered in C<OLD>. The next read operation on C<NEW> will
+return the same data as the corresponding operation on C<OLD>.
+Formerly, it would have returned the data from the start of the
+following disk block instead.
+
=head1 Supported Platforms
=over 4
=over 4
+=item ByteLoader
+
+The ByteLoader is a dedication extension to generate and run
+Perl bytecode. See L<ByteLoader>.
+
+=item B
+
+The Perl Compiler suite has been extensively reworked for this
+release.
+
+=item Devel::DProf
+
+Devel::DProf, a Perl source code profiler has been added.
+
=item Dumpvalue
Added Dumpvalue module provides screen dumps of Perl data.
from the caller's context. C<encoding> is currently the only supported
attribute.
-Lexical warnings pragma, C<use warning;>, to control optional warnings.
+Lexical warnings pragma, C<use warnings;>, to control optional warnings.
C<use filetest> to control the behaviour of filetests (C<-r> C<-w> ...).
Currently only one subpragma implemented, "use filetest 'access';",
by Perl. This combination appears in an interpolated variable or a
C<'>-delimited regular expression.
-=item Unrecognized escape \\%c passed through
+=item Filehandle %s opened only for output
-(W) You used a backslash-character combination which is not recognized
-by Perl.
+(W) You tried to read from a filehandle opened only for writing. If you
+intended it to be a read-write filehandle, you needed to open it with
+"+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
+you intended only to read from the file, use "E<lt>". See
+L<perlfunc/open>.
=item Missing command in piped open
(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
construction, but the command was missing or blank.
+=item Unrecognized escape \\%c passed through
+
+(W) You used a backslash-character combination which is not recognized
+by Perl.
+
=item defined(@array) is deprecated
(D) defined() is not usually useful on arrays because it checks for an
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