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=head1 NAME
perl571delta - what's new for perl v5.7.1
=head1 DESCRIPTION
This document describes differences between the 5.7.0 release and the
5.7.1 release.
(To view the differences between the 5.6.0 release and the 5.7.0
release, see L<perl570delta>).
=head1 Incompatible Changes
=over 4
=item *
Although "you shouldn't do that", it was possible to write code that
depends on Perl's hashed key order (Data::Dumper does this). The new
algorithm "One-at-a-Time" produces a different hashed key order.
More details are in L<perldelta/Performance Enhancements>.
=back
=head1 Core Enhancements
=over 4
=item *
Anonymous temporary files are available without need to
'use FileHandle' or other module via
open($fh,"+>", undef) || ...
=item *
IO is now by default done via PerlIO rather than system's "stdio".
PerlIO allows "layers" to be "pushed" onto a file handle to alter the
handle's behaviour. Layers can be specified at open time via 3-arg
form of open:
open($fh,'>:crlf :utf8', $path) || ...
or on already opened handles via extended C<binmode>:
binmode($fh,':encoding(iso-8859-7)');
The built-in layers are: unix (low level read/write), stdio (as in
previous Perls), perlio (re-implementation of stdio buffering in a
portable manner), crlf (does CRLF <=> "\n" translation as on Win32,
but available on any platform). A mmap layer may be available if
platform supports it (mostly UNIXes).
Layers to be applied by default may be specified via the 'open' pragma.
=item *
File handles can be marked as accepting Perl's internal encoding of Unicode
(UTF-8 or UTF-EBCDIC depending on platfrom) by a pseudo layer ":utf8" :
open($fh,">:utf8","Uni.txt");
=item *
File handles can translate character encodings from/to Perl's internal
Unicode form on read/write via the ":encoding()" layer.
=item *
File handles can be opened to "in memory" files held in Perl scalars via:
open($fh,'>', \$variable) || ...
=item *
Formats now support zero-padded decimal fields.
=item *
The list form of C<open> is now implemented for pipes (at least on UNIX):
open($fh,"-|", 'cat', '/etc/motd')
creates a pipe, and runs the equivalent of exec('cat', '/etc/motd') in
the child process.
=item *
The printf and sprintf now support parameter reordering using the
C<%\d+\$> and C<*\d+\$> syntaxes.
=back
=head1 Performance Enhancements
=over 4
=item *
Hashes now use Bob Jenkins "One-at-a-Time" hashing key algorithm
(http://burtleburtle.net/bob/hash/doobs.html).
This algorithm is reasonably fast while producing a much better spread
of values. Hash values output from the algorithm on a hash of all
3-char printable ASCII keys comes much closer to passing the DIEHARD
random number generation tests. According to perlbench, this change
has not affected the overall speed of Perl.
=back
=head1 Installation and Configuration Improvements
=over 4
=item *
Configure no longer includes the DBM libraries (dbm, gdbm, db, ndbm)
when building the Perl binary. The only exception to this is SunOS 4.x,
which needs them.
=back
=head1 Selected Bug Fixes
=over 4
=item *
vec() now tries to work with characters <= 255 when possible, but it leaves
higher character values in place. In that case, if vec() was used to modify
the string, it is no longer considered to be utf8-encoded.
=back
=head1 Core Enhancements
=head2 New Modules
=over 4
=item *
Encode provides a mechanism to translate between different character
encodings. Support for Unicode, ISO-8859-*, ASCII, CP*, KOI8-R, and
three variants of EBCDIC are compiled in to the module. Several other
encodings (like Japanese, Chinese, and MacIntosh encodings) are
included and will be loaded at runtime.
=item *
Any encoding supported by Encode module is also available to the
":encoding()" layer if PerlIO is used.
=item *
PerlIO::Scalar provides the IO to "in memory" perl scalars discussed
above. It also serves as an example of a loadable layer.
=item *
PerlIO::Via acts as a PerlIO layer and wraps PerlIO layer
functionality provided by a class (typically implemented in
perl code).
=item *
MIME::QuotedPrint has been enhanced to provide the basic methods
necessary to use it with PerlIO::Via as in :
use MIME::QuotedPrint;
open($fh,">Via(MIME::QuotedPrint)",$path)
=back
=head2 Updated And Improved Modules and Pragmata
=over 4
=item *
The C<open> pragma allows layers other than ":raw" and ":crlf" when
using PerlIO.
=item *
The utf8:: name space (as in the pragma) provides various
Perl-callable functions to provide low level access to Perl's
internal Unicode representation.
=back
=head1 Known Problems
=head2 sprintf tests 129 and 130
The op/sprintf tests 129 and 130 are known to fail in some platforms.
Examples include any platform using sfio, and Tandem's NonStop-UX.
The failing platforms do not comply with the ANSI C Standard, line
19ff on page 134 of ANSI X3.159 1989 to be exact. (They produce
something else than "1" and "-1" when formatting 0.6 and -0.6 using
the printf format "%.0f", most often they produce "0" and "-0".)
=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.com/perl/, 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.
=head1 HISTORY
Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
from The Perl Porters and Perl Users submitting feedback and patches.
Send omissions or corrections to <F<perlbug@perl.org>>.
=cut
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