perl572delta.pod

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

=head1 NAME

perl572delta - what's new for perl v5.7.2

=head1 DESCRIPTION

This document describes differences between the 5.7.1 release and the
5.7.2 release.  

(To view the differences between the 5.6.0 release and the 5.7.0
release, see L<perl570delta>.  To view the differences between the
5.7.0 release and the 5.7.1 release, see L<perl571delta>.)

=head1 Security Vulnerability Closed

(This change was already made in 5.7.0 but bears repeating here.)

A security vulnerability affecting all Perl versions prior to 5.6.1
was found in August 2000.  The vulnerability does not affect default
installations and as far as is known affects only the Linux platform.

You should upgrade your Perl to 5.6.1 as soon as possible.  Patches
for earlier releases exist but using the patches require full
recompilation from the source code anyway, so 5.6.1 is your best
choice.

See http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt
for more information.

=head1 Incompatible Changes

=head2 64-bit platforms and malloc

If your pointers are 64 bits wide, the Perl malloc is no more being
used because it simply does not work with 8-byte pointers.  Also,
usually the system malloc on such platforms are much better optimized
for such large memory models than the Perl malloc.

=head2 AIX Dynaloading

The AIX dynaloading now uses in AIX releases 4.3 and newer the native
dlopen interface of AIX instead of the old emulated interface.  This
change will probably break backward compatibility with compiled
modules.  The change was made to make Perl more compliant with other
applications like modperl which are using the AIX native interface.

=head2 Socket Extension Dynamic in VMS

The Socket extension is now dynamically loaded instead of being
statically built in.  This may or may not be a problem with ancient
TCP/IP stacks of VMS: we do not know since we weren't able to test
Perl in such configurations.

=head2 Different Definition of the Unicode Character Classes \p{In...}

As suggested by the Unicode consortium, the Unicode character classes
now prefer I<scripts> as opposed to I<blocks> (as defined by Unicode);
in Perl, when the C<\p{In....}> and the C<\p{In....}> regular expression
constructs are used.  This has changed the definition of some of those
character classes.

The difference between scripts and blocks is that scripts are the
glyphs used by a language or a group of languages, while the blocks
are more artificial groupings of 256 characters based on the Unicode
numbering.

In general this change results in more inclusive Unicode character
classes, but changes to the other direction also do take place:
for example while the script C<Latin> includes all the Latin
characters and their various diacritic-adorned versions, it
does not include the various punctuation or digits (since they
are not solely C<Latin>).

Changes in the character class semantics may have happened if a script
and a block happen to have the same name, for example C<Hebrew>.
In such cases the script wins and C<\p{InHebrew}> now means the script
definition of Hebrew.  The block definition in still available,
though, by appending C<Block> to the name: C<\p{InHebrewBlock}> means
what C<\p{InHebrew}> meant in perl 5.6.0.  For the full list
of affected character classes, see L<perlunicode/Blocks>.

=head2 Deprecations

The current user-visible implementation of pseudo-hashes (the weird
use of the first array element) is deprecated starting from Perl 5.8.0
and will be removed in Perl 5.10.0, and the feature will be
implemented differently.  Not only is the current interface rather
ugly, but the current implementation slows down normal array and hash
use quite noticeably. The C<fields> pragma interface will remain
available.

The syntaxes C<< @a->[...] >> and  C<< @h->{...} >> have now been deprecated.

The suidperl is also considered to be too much a risk to continue
maintaining and the suidperl code is likely to be removed in a future
release.

The C<package;> syntax (C<package> without an argument has been
deprecated.  Its semantics were never that clear and its
implementation even less so.  If you have used that feature to
disallow all but fully qualified variables, C<use strict;> instead.

The chdir(undef) and chdir('') behaviors to match chdir() has been
deprecated.  In future versions, chdir(undef) and chdir('') will
simply fail.

=head1 Core Enhancements

In general a lot of fixing has happened in the area of Perl's
understanding of numbers, both integer and floating point.  Since in
many systems the standard number parsing functions like C<strtoul()>
and C<atof()> seem to have bugs, Perl tries to work around their
deficiencies.  This results hopefully in more accurate numbers.

=over 4

=item *

The rules for allowing underscores (underbars) in numeric constants
have been relaxed and simplified: now you can have an underscore
B<between digits>.

=item *

GMAGIC (right-hand side magic) could in many cases such as string
concatenation be invoked too many times.

=item *

Lexicals I: lexicals outside an eval "" weren't resolved
correctly inside a subroutine definition inside the eval "" if they
were not already referenced in the top level of the eval""ed code.

=item *

Lexicals II: lexicals leaked at file scope into subroutines that
were declared before the lexicals.

=item *

Lvalue subroutines can now return C<undef> in list context.

=item *

The C<op_clear> and C<op_null> are now exported.

=item *

A new special regular expression variable has been introduced:
C<$^N>, which contains the most-recently closed group (submatch).

=item *

L<utime> now supports C<utime undef, undef, @files> to change the
file timestamps to the current time.

=item *

The Perl parser has been stress tested using both random input and
Markov chain input.

=item *

C<eval "v200"> now works.

=item *

VMS now works under PerlIO.

=item *

END blocks are now run even if you exit/die in a BEGIN block.
The execution of END blocks is now controlled by 
PL_exit_flags & PERL_EXIT_DESTRUCT_END. This enables the new
behaviour for perl embedders. This will default in 5.10. See
L<perlembed>.

=back

=head1 Modules and Pragmata

=head2 New Modules and Distributions

=over 4

=item *

L<Attribute::Handlers> - Simpler definition of attribute handlers

=item *

L<ExtUtils::Constant> - generate XS code to import C header constants

=item *

L<I18N::Langinfo> - query locale information

=item *

L<I18N::LangTags> - functions for dealing with RFC3066-style language tags

=item *

L<libnet> - a collection of perl5 modules related to network programming

Perl installation leaves libnet unconfigured, use F<libnetcfg> to configure.

=item *

L<List::Util> - selection of general-utility list subroutines

=item *

L<Locale::Maketext> - framework for localization

=item *

L<Memoize> - Make your functions faster by trading space for time

=item *

L<NEXT> - pseudo-class for method redispatch

=item *

L<Scalar::Util> - selection of general-utility scalar subroutines

=item *

L<Test::More> - yet another framework for writing test scripts

=item *

L<Test::Simple> - Basic utilities for writing tests

=item *

L<Time::HiRes> - high resolution ualarm, usleep, and gettimeofday

=item *

L<Time::Piece> - Object Oriented time objects

(Previously known as L<Time::Object>.)

=item *

L<Time::Seconds> - a simple API to convert seconds to other date values

=item *

L<UnicodeCD> - Unicode Character Database

=back

=head2 Updated And Improved Modules and Pragmata

=over 4

=item *

L<B::Deparse> module has been significantly enhanced.  It now
can deparse almost all of the standard test suite (so that the
tests still succeed).  There is a make target "test.deparse"
for trying this out.

=item *

L<Class::Struct> now assigns the array/hash element if the accessor
is called with an array/hash element as the B<sole> argument.

=item *

L<Cwd> extension is now (even) faster.

=item *

L<DB_File> extension has been updated to version 1.77.

=item *

L<Fcntl>, L<Socket>, and L<Sys::Syslog> have been rewritten to use the
new-style constant dispatch section (see L<ExtUtils::Constant>).

=item *

L<File::Find> is now (again) reentrant.  It also has been made
more portable.

=item *

L<File::Glob> now supports C<GLOB_LIMIT> constant to limit the
size of the returned list of filenames.

=item *

L<IO::Socket::INET> now supports C<LocalPort> of zero (usually meaning
that the operating system will make one up.)

=item *

The L<vars> pragma now supports declaring fully qualified variables.
(Something that C<our()> does not and will not support.)

=back

=head1 Utility Changes

=over 4

=item *

The F<emacs/e2ctags.pl> is now much faster.

=item *

L<h2ph> now supports C trigraphs.

=item *

L<h2xs> uses the new L<ExtUtils::Constant> module which will affect
newly created extensions that define constants.  Since the new code is
more correct (if you have two constants where the first one is a
prefix of the second one, the first constant B<never> gets defined),
less lossy (it uses integers for integer constant, as opposed to the
old code that used floating point numbers even for integer constants),
and slightly faster, you might want to consider regenerating your
extension code (the new scheme makes regenerating easy).
L<h2xs> now also supports C trigraphs.

=item *

L<libnetcfg> has been added to configure the libnet.

=item *

The F<Pod::Html> (and thusly L<pod2html>) now allows specifying
a cache directory.

=back

=head1 New Documentation

=over 4

=item *

L<Locale::Maketext::TPJ13> is an article about software localization,
originally published in The Perl Journal #13, republished here with
kind permission.

=item *

More README.$PLATFORM files have been converted into pod, which also
means that they also be installed as perl$PLATFORM documentation
files.  The new files are L<perlapollo>, L<perlbeos>, L<perldgux>,
L<perlhurd>, L<perlmint>, L<perlnetware>, L<perlplan9>, L<perlqnx>,
and L<perltru64>.

=item *

The F<Todo> and F<Todo-5.6> files have been merged into L<perltodo>.

=item *

Use of the F<gprof> tool to profile Perl has been documented in
L<perlhack>.  There is a make target "perl.gprof" for generating a
gprofiled Perl executable.

=back

=head1 Installation and Configuration Improvements

=head2 New Or Improved Platforms

=over 4

=item *

AIX should now work better with gcc, threads, and 64-bitness.  Also the
long doubles support in AIX should be better now.  See L<perlaix>.

=item *

AtheOS ( http://www.atheos.cx/ ) is a new platform.

=item *

DG/UX platform now supports the 5.005-style threads.  See L<perldgux>.

=item *

DYNIX/ptx platform (a.k.a. dynixptx) is supported at or near osvers 4.5.2.

=item *

Several Mac OS (Classic) portability patches have been applied.  We
hope to get a fully working port by 5.8.0.  (The remaining problems
relate to the changed IO model of Perl.)  See L<perlmacos>.

=item *

Mac OS X (or Darwin) should now be able to build Perl even on HFS+
filesystems.  (The case-insensitivity confused the Perl build process.)

=item *

NetWare from Novell is now supported.  See L<perlnetware>.

=item *

The Amdahl UTS UNIX mainframe platform is now supported.

=back

=head2 Generic Improvements