perl5100delta.1

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.

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.\" ========================================================================
.\"
.IX Title "PERL5100DELTA 1"
.TH PERL5100DELTA 1 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
perldelta \- what is new for perl 5.10.0
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This document describes the differences between the 5.8.8 release and
the 5.10.0 release.
.PP
Many of the bug fixes in 5.10.0 were already seen in the 5.8.X maintenance
releases; they are not duplicated here and are documented in the set of
man pages named perl58[1\-8]?delta.
.SH "Core Enhancements"
.IX Header "Core Enhancements"
.ie n .Sh "The ""feature"" pragma"
.el .Sh "The \f(CWfeature\fP pragma"
.IX Subsection "The feature pragma"
The \f(CW\*(C`feature\*(C'\fR pragma is used to enable new syntax that would break Perl's
backwards-compatibility with older releases of the language. It's a lexical
pragma, like \f(CW\*(C`strict\*(C'\fR or \f(CW\*(C`warnings\*(C'\fR.
.PP
Currently the following new features are available: \f(CW\*(C`switch\*(C'\fR (adds a
switch statement), \f(CW\*(C`say\*(C'\fR (adds a \f(CW\*(C`say\*(C'\fR built-in function), and \f(CW\*(C`state\*(C'\fR
(adds a \f(CW\*(C`state\*(C'\fR keyword for declaring \*(L"static\*(R" variables). Those
features are described in their own sections of this document.
.PP
The \f(CW\*(C`feature\*(C'\fR pragma is also implicitly loaded when you require a minimal
perl version (with the \f(CW\*(C`use VERSION\*(C'\fR construct) greater than, or equal
to, 5.9.5. See feature for details.
.Sh "New \fB\-E\fP command-line switch"
.IX Subsection "New -E command-line switch"
\&\fB\-E\fR is equivalent to \fB\-e\fR, but it implicitly enables all
optional features (like \f(CW\*(C`use feature ":5.10"\*(C'\fR).
.Sh "Defined-or operator"
.IX Subsection "Defined-or operator"
A new operator \f(CW\*(C`//\*(C'\fR (defined-or) has been implemented.
The following expression:
.PP
.Vb 1
\&    $a // $b
.Ve
.PP
is merely equivalent to
.PP
.Vb 1
\&   defined $a ? $a : $b
.Ve
.PP
and the statement
.PP
.Vb 1
\&   $c //= $d;
.Ve
.PP
can now be used instead of
.PP
.Vb 1
\&   $c = $d unless defined $c;
.Ve
.PP
The \f(CW\*(C`//\*(C'\fR operator has the same precedence and associativity as \f(CW\*(C`||\*(C'\fR.
Special care has been taken to ensure that this operator Do What You Mean
while not breaking old code, but some edge cases involving the empty
regular expression may now parse differently.  See perlop for
details.
.Sh "Switch and Smart Match operator"
.IX Subsection "Switch and Smart Match operator"
Perl 5 now has a switch statement. It's available when \f(CW\*(C`use feature
\&\*(Aqswitch\*(Aq\*(C'\fR is in effect. This feature introduces three new keywords,
\&\f(CW\*(C`given\*(C'\fR, \f(CW\*(C`when\*(C'\fR, and \f(CW\*(C`default\*(C'\fR:
.PP
.Vb 6
\&    given ($foo) {
\&        when (/^abc/) { $abc = 1; }
\&        when (/^def/) { $def = 1; }
\&        when (/^xyz/) { $xyz = 1; }
\&        default { $nothing = 1; }
\&    }
.Ve
.PP
A more complete description of how Perl matches the switch variable
against the \f(CW\*(C`when\*(C'\fR conditions is given in \*(L"Switch statements\*(R" in perlsyn.
.PP
This kind of match is called \fIsmart match\fR, and it's also possible to use
it outside of switch statements, via the new \f(CW\*(C`~~\*(C'\fR operator. See
\&\*(L"Smart matching in detail\*(R" in perlsyn.
.PP
This feature was contributed by Robin Houston.
.Sh "Regular expressions"
.IX Subsection "Regular expressions"
.IP "Recursive Patterns" 4
.IX Item "Recursive Patterns"
It is now possible to write recursive patterns without using the \f(CW\*(C`(??{})\*(C'\fR
construct. This new way is more efficient, and in many cases easier to
read.
.Sp
Each capturing parenthesis can now be treated as an independent pattern
that can be entered by using the \f(CW\*(C`(?PARNO)\*(C'\fR syntax (\f(CW\*(C`PARNO\*(C'\fR standing for
\&\*(L"parenthesis number\*(R"). For example, the following pattern will match
nested balanced angle brackets:
.Sp
.Vb 10
\&    /
\&     ^                      # start of line
\&     (                      # start capture buffer 1
\&        <                   #   match an opening angle bracket
\&        (?:                 #   match one of:
\&            (?>             #     don\*(Aqt backtrack over the inside of this group
\&                [^<>]+      #       one or more non angle brackets
\&            )               #     end non backtracking group
\&        |                   #     ... or ...
\&            (?1)            #     recurse to bracket 1 and try it again
\&        )*                  #   0 or more times.
\&        >                   #   match a closing angle bracket
\&     )                      # end capture buffer one
\&     $                      # end of line
\&    /x
.Ve
.Sp
\&\s-1PCRE\s0 users should note that Perl's recursive regex feature allows
backtracking into a recursed pattern, whereas in \s-1PCRE\s0 the recursion is
atomic or \*(L"possessive\*(R" in nature.  As in the example above, you can
add (?>) to control this selectively.  (Yves Orton)
.IP "Named Capture Buffers" 4
.IX Item "Named Capture Buffers"
It is now possible to name capturing parenthesis in a pattern and refer to
the captured contents by name. The naming syntax is \f(CW\*(C`(?<NAME>....)\*(C'\fR.
It's possible to backreference to a named buffer with the \f(CW\*(C`\ek<NAME>\*(C'\fR
syntax. In code, the new magical hashes \f(CW\*(C`%+\*(C'\fR and \f(CW\*(C`%\-\*(C'\fR can be used to
access the contents of the capture buffers.
.Sp
Thus, to replace all doubled chars with a single copy, one could write
.Sp
.Vb 1
\&    s/(?<letter>.)\ek<letter>/$+{letter}/g
.Ve
.Sp
Only buffers with defined contents will be \*(L"visible\*(R" in the \f(CW\*(C`%+\*(C'\fR hash, so