perl56delta.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.

interpreter threads).  C<use Thread;> continues to be available when you
specify the -Duse5005threads option to Configure, bugs and all.

    NOTE: Support for threads continues to be an experimental feature.
    Interfaces and implementation are subject to sudden and drastic changes.

=head2 New Configure flags

The following new flags may be enabled on the Configure command line
by running Configure with C<-Dflag>.

    usemultiplicity
    usethreads useithreads	(new interpreter threads: no Perl API yet)
    usethreads use5005threads	(threads as they were in 5.005)

    use64bitint			(equal to now deprecated 'use64bits')
    use64bitall

    uselongdouble
    usemorebits
    uselargefiles
    usesocks			(only SOCKS v5 supported)

=head2 Threadedness and 64-bitness now more daring

The Configure options enabling the use of threads and the use of
64-bitness are now more daring in the sense that they no more have an
explicit list of operating systems of known threads/64-bit
capabilities.  In other words: if your operating system has the
necessary APIs and datatypes, you should be able just to go ahead and
use them, for threads by Configure -Dusethreads, and for 64 bits
either explicitly by Configure -Duse64bitint or implicitly if your
system has 64-bit wide datatypes.  See also L<"64-bit support">.

=head2 Long Doubles

Some platforms have "long doubles", floating point numbers of even
larger range than ordinary "doubles".  To enable using long doubles for
Perl's scalars, use -Duselongdouble.

=head2 -Dusemorebits

You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
See also L<"64-bit support">.

=head2 -Duselargefiles

Some platforms support system APIs that are capable of handling large files
(typically, files larger than two gigabytes).  Perl will try to use these
APIs if you ask for -Duselargefiles.

See L<"Large file support"> for more information. 

=head2 installusrbinperl

You can use "Configure -Uinstallusrbinperl" which causes installperl
to skip installing perl also as /usr/bin/perl.  This is useful if you
prefer not to modify /usr/bin for some reason or another but harmful
because many scripts assume to find Perl in /usr/bin/perl.

=head2 SOCKS support

You can use "Configure -Dusesocks" which causes Perl to probe
for the SOCKS proxy protocol library (v5, not v4).  For more information
on SOCKS, see:

    http://www.socks.nec.com/

=head2 C<-A> flag

You can "post-edit" the Configure variables using the Configure C<-A>
switch.  The editing happens immediately after the platform specific
hints files have been processed but before the actual configuration
process starts.  Run C<Configure -h> to find out the full C<-A> syntax.

=head2 Enhanced Installation Directories

The installation structure has been enriched to improve the support
for maintaining multiple versions of perl, to provide locations for
vendor-supplied modules, scripts, and manpages, and to ease maintenance
of locally-added modules, scripts, and manpages.  See the section on
Installation Directories in the INSTALL file for complete details.
For most users building and installing from source, the defaults should
be fine.

If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
special values for library directories, you might wish to consider using
the new C<-Dsiteprefix> setting instead.  Also, if you wish to re-use a
config.sh file from an earlier version of perl, you should be sure to
check that Configure makes sensible choices for the new directories.
See INSTALL for complete details.

=head1 Platform specific changes

=head2 Supported platforms

=over 4

=item *

The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
extension.

=item *

GNU/Hurd is now supported.

=item *

Rhapsody/Darwin is now supported.

=item *

EPOC is now supported (on Psion 5).

=item *

The cygwin port (formerly cygwin32) has been greatly improved.

=back

=head2 DOS

=over 4

=item *

Perl now works with djgpp 2.02 (and 2.03 alpha).

=item *

Environment variable names are not converted to uppercase any more.

=item *

Incorrect exit codes from backticks have been fixed.

=item *

This port continues to use its own builtin globbing (not File::Glob).

=back

=head2 OS390 (OpenEdition MVS)

Support for this EBCDIC platform has not been renewed in this release.
There are difficulties in reconciling Perl's standardization on UTF-8
as its internal representation for characters with the EBCDIC character
set, because the two are incompatible.

It is unclear whether future versions will renew support for this
platform, but the possibility exists.

=head2 VMS

Numerous revisions and extensions to configuration, build, testing, and
installation process to accommodate core changes and VMS-specific options.

Expand %ENV-handling code to allow runtime mapping to logical names,
CLI symbols, and CRTL environ array.

Extension of subprocess invocation code to accept filespecs as command
"verbs".

Add to Perl command line processing the ability to use default file types and
to recognize Unix-style C<2E<gt>&1>.

Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.

Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.

Barewords at start of Unix-syntax paths may be treated as text rather than
only as logical names.

Optional secure translation of several logical names used internally by Perl.

Miscellaneous bugfixing and porting of new core code to VMS.

Thanks are gladly extended to the many people who have contributed VMS
patches, testing, and ideas.

=head2 Win32

Perl can now emulate fork() internally, using multiple interpreters running
in different concurrent threads.  This support must be enabled at build
time.  See L<perlfork> for detailed information.

When given a pathname that consists only of a drivename, such as C<A:>,
opendir() and stat() now use the current working directory for the drive
rather than the drive root.

The builtin XSUB functions in the Win32:: namespace are documented.  See
L<Win32>.

$^X now contains the full path name of the running executable.

A Win32::GetLongPathName() function is provided to complement
Win32::GetFullPathName() and Win32::GetShortPathName().  See L<Win32>.

POSIX::uname() is supported.

system(1,...) now returns true process IDs rather than process
handles.  kill() accepts any real process id, rather than strictly
return values from system(1,...).

For better compatibility with Unix, C<kill(0, $pid)> can now be used to
test whether a process exists.

The C<Shell> module is supported.

Better support for building Perl under command.com in Windows 95
has been added.

Scripts are read in binary mode by default to allow ByteLoader (and
the filter mechanism in general) to work properly.  For compatibility,
the DATA filehandle will be set to text mode if a carriage return is
detected at the end of the line containing the __END__ or __DATA__
token; if not, the DATA filehandle will be left open in binary mode.
Earlier versions always opened the DATA filehandle in text mode.

The glob() operator is implemented via the C<File::Glob> extension,
which supports glob syntax of the C shell.  This increases the flexibility
of the glob() operator, but there may be compatibility issues for
programs that relied on the older globbing syntax.  If you want to
preserve compatibility with the older syntax, you might want to run
perl with C<-MFile::DosGlob>.  For details and compatibility information,
see L<File::Glob>.

=head1 Significant bug fixes

=head2 <HANDLE> on empty files

With C<$/> set to C<undef>, "slurping" an empty file returns a string of
zero length (instead of C<undef>, as it used to) the first time the
HANDLE is read after C<$/> is set to C<undef>.  Further reads yield
C<undef>.

This means that the following will append "foo" to an empty file (it used
to do nothing):

    perl -0777 -pi -e 's/^/foo/' empty_file

The behaviour of:

    perl -pi -e 's/^/foo/' empty_file

is unchanged (it continues to leave the file empty).

=head2 C<eval '...'> improvements

Line numbers (as reflected by caller() and most diagnostics) within
C<eval '...'> were often incorrect where here documents were involved.
This has been corrected.

Lexical lookups for variables appearing in C<eval '...'> within
functions that were themselves called within an C<eval '...'> were
searching the wrong place for lexicals.  The lexical search now
correctly ends at the subroutine's block boundary.

The use of C<return> within C<eval {...}> caused $@ not to be reset
correctly when no exception occurred within the eval.  This has
been fixed.

Parsing of here documents used to be flawed when they appeared as
the replacement expression in C<eval 's/.../.../e'>.  This has
been fixed.

=head2 All compilation errors are true errors

Some "errors" encountered at compile time were by necessity 
generated as warnings followed by eventual termination of the
program.  This enabled more such errors to be reported in a
single run, rather than causing a hard stop at the first error
that was encountered.

The mechanism for reporting such errors has been reimplemented
to queue compile-time errors and report them at the end of the
compilation as true errors rather than as warnings.  This fixes
cases where error messages leaked through in the form of warnings
when code was compiled at run time using C<eval STRING>, and
also allows such errors to be reliably trapped using C<eval "...">.

=head2 Implicitly closed filehandles are safer

Sometimes implicitly closed filehandles (as when they are localized,
and Perl automatically closes them on exiting the scope) could
inadvertently set $? or $!.  This has been corrected.


=head2 Behavior of list slices is more consistent

When taking a slice of a literal list (as opposed to a slice of
an array or hash), Perl used to return an empty list if the
result happened to be composed of all undef values.

The new behavior is to produce an empty list if (and only if)
the original list was empty.  Consider the following example:

    @a = (1,undef,undef,2)[2,1,2];

The old behavior would have resulted in @a having no elements.
The new behavior ensures it has three undefined elements.

Note in particular that the behavior of slices of the following
cases remains unchanged:

    @a = ()[1,2];
    @a = (getpwent)[7,0];
    @a = (anything_returning_empty_list())[2,1,2];
    @a = @b[2,1,2];
    @a = @c{'a','b','c'};

See L<perldata>.

=head2 C<(\$)> prototype and C<$foo{a}>

A scalar reference prototype now correctly allows a hash or
array element in that slot.

=head2 C<goto &sub> and AUTOLOAD

The C<goto &sub> construct works correctly when C<&sub> happens
to be autoloaded.

=head2 C<-bareword> allowed under C<use integer>

The autoquoting of barewords preceded by C<-> did not work
in prior versions when the C<integer> pragma was enabled.
This has been fixed.

=head2 Failures in DESTROY()

When code in a destructor threw an exception, it went unnoticed
in earlier versions of Perl, unless someone happened to be
looking in $@ just after the point the destructor happened to
run.  Such failures are now visible as warnings when warnings are
enabled.

=head2 Locale bugs fixed

printf() and sprintf() previously reset the numeric locale
back to the default "C" locale.  This has been fixed.

Numbers formatted according to the local numeric locale
(such as using a decimal comma instead of a decimal dot) caused
"isn't numeric" warnings, even while the operations accessing
those numbers produced correct results.  These warnings have been
discontinued.

=head2 Memory leaks

The C<eval 'return sub {...}'> construct could sometimes leak
memory.  This has been fixed.

Operations that aren't filehandle constructors used to leak memory
when used on invalid filehandles.  This has been fixed.

Constructs that modified C<@_> could fail to deallocate values
in C<@_> and thus leak memory.  This has been corrected.

=head2 Spurious subroutine stubs after failed subroutine calls

Perl could sometimes create empty subroutine stubs when a
subroutine was not found in the