perlvar.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.

it really means
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.Vb 1
\&    $foo{join($;, $a, $b, $c)}
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But don't put
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.Vb 1
\&    @foo{$a,$b,$c}      # a slice\-\-note the @
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which means
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.Vb 1
\&    ($foo{$a},$foo{$b},$foo{$c})
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Default is \*(L"\e034\*(R", the same as \s-1SUBSEP\s0 in \fBawk\fR.  If your
keys contain binary data there might not be any safe value for \f(CW$;\fR.
(Mnemonic: comma (the syntactic subscript separator) is a
semi-semicolon.  Yeah, I know, it's pretty lame, but \f(CW$,\fR is already
taken for something more important.)
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Consider using \*(L"real\*(R" multidimensional arrays as described
in perllol.
.IP "\s-1HANDLE\-\s0>format_page_number(\s-1EXPR\s0)" 8
.IX Item "HANDLE->format_page_number(EXPR)"
.PD 0
.ie n .IP "$FORMAT_PAGE_NUMBER" 8
.el .IP "\f(CW$FORMAT_PAGE_NUMBER\fR" 8
.IX Item "$FORMAT_PAGE_NUMBER"
.IP "$%" 8
.IX Xref "$% $FORMAT_PAGE_NUMBER"
.PD
The current page number of the currently selected output channel.
Used with formats.
(Mnemonic: % is page number in \fBnroff\fR.)
.IP "\s-1HANDLE\-\s0>format_lines_per_page(\s-1EXPR\s0)" 8
.IX Item "HANDLE->format_lines_per_page(EXPR)"
.PD 0
.ie n .IP "$FORMAT_LINES_PER_PAGE" 8
.el .IP "\f(CW$FORMAT_LINES_PER_PAGE\fR" 8
.IX Item "$FORMAT_LINES_PER_PAGE"
.IP "$=" 8
.IX Xref "$= $FORMAT_LINES_PER_PAGE"
.PD
The current page length (printable lines) of the currently selected
output channel.  Default is 60.  
Used with formats.
(Mnemonic: = has horizontal lines.)
.IP "\s-1HANDLE\-\s0>format_lines_left(\s-1EXPR\s0)" 8
.IX Item "HANDLE->format_lines_left(EXPR)"
.PD 0
.ie n .IP "$FORMAT_LINES_LEFT" 8
.el .IP "\f(CW$FORMAT_LINES_LEFT\fR" 8
.IX Item "$FORMAT_LINES_LEFT"
.IP "$\-" 8
.IX Xref "$- $FORMAT_LINES_LEFT"
.PD
The number of lines left on the page of the currently selected output
channel.  
Used with formats.
(Mnemonic: lines_on_page \- lines_printed.)
.ie n .IP "@LAST_MATCH_START" 8
.el .IP "\f(CW@LAST_MATCH_START\fR" 8
.IX Item "@LAST_MATCH_START"
.PD 0
.IP "@\-" 8
.IX Xref "@- @LAST_MATCH_START"
.PD
$\-[0] is the offset of the start of the last successful match.
\&\f(CW\*(C`$\-[\*(C'\fR\fIn\fR\f(CW\*(C`]\*(C'\fR is the offset of the start of the substring matched by
\&\fIn\fR\-th subpattern, or undef if the subpattern did not match.
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Thus after a match against \f(CW$_\fR, $& coincides with \f(CW\*(C`substr $_, $\-[0],
$+[0] \- $\-[0]\*(C'\fR.  Similarly, $\fIn\fR coincides with \f(CW\*(C`substr $_, $\-[n],
$+[n] \- $\-[n]\*(C'\fR if \f(CW\*(C`$\-[n]\*(C'\fR is defined, and $+ coincides with
\&\f(CW\*(C`substr $_, $\-[$#\-], $+[$#\-] \- $\-[$#\-]\*(C'\fR.  One can use \f(CW\*(C`$#\-\*(C'\fR to find the last
matched subgroup in the last successful match.  Contrast with
\&\f(CW$#+\fR, the number of subgroups in the regular expression.  Compare
with \f(CW\*(C`@+\*(C'\fR.
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This array holds the offsets of the beginnings of the last
successful submatches in the currently active dynamic scope.
\&\f(CW\*(C`$\-[0]\*(C'\fR is the offset into the string of the beginning of the
entire match.  The \fIn\fRth element of this array holds the offset
of the \fIn\fRth submatch, so \f(CW\*(C`$\-[1]\*(C'\fR is the offset where \f(CW$1\fR
begins, \f(CW\*(C`$\-[2]\*(C'\fR the offset where \f(CW$2\fR begins, and so on.
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After a match against some variable \f(CW$var:\fR
.RS 8
.ie n .IP """$\`""\fR is the same as \f(CW""substr($var, 0, $\-[0])""" 5
.el .IP "\f(CW$\`\fR is the same as \f(CWsubstr($var, 0, $\-[0])\fR" 5
.IX Item "$ is the same as substr($var, 0, $-[0])"
.PD 0
.ie n .IP "$&\fR is the same as \f(CW""substr($var, $\-[0], $+[0] \- $\-[0])""" 5
.el .IP "\f(CW$&\fR is the same as \f(CWsubstr($var, $\-[0], $+[0] \- $\-[0])\fR" 5
.IX Item "$& is the same as substr($var, $-[0], $+[0] - $-[0])"
.ie n .IP """$\*(Aq""\fR is the same as \f(CW""substr($var, $+[0])""" 5
.el .IP "\f(CW$\*(Aq\fR is the same as \f(CWsubstr($var, $+[0])\fR" 5
.IX Item "$ is the same as substr($var, $+[0])"
.ie n .IP "$1\fR is the same as \f(CW""substr($var, $\-[1], $+[1] \- $\-[1])""" 5
.el .IP "\f(CW$1\fR is the same as \f(CWsubstr($var, $\-[1], $+[1] \- $\-[1])\fR" 5
.IX Item "$1 is the same as substr($var, $-[1], $+[1] - $-[1])"
.ie n .IP "$2\fR is the same as \f(CW""substr($var, $\-[2], $+[2] \- $\-[2])""" 5
.el .IP "\f(CW$2\fR is the same as \f(CWsubstr($var, $\-[2], $+[2] \- $\-[2])\fR" 5
.IX Item "$2 is the same as substr($var, $-[2], $+[2] - $-[2])"
.ie n .IP "$3\fR is the same as \f(CW""substr($var, $\-[3], $+[3] \- $\-[3])""" 5
.el .IP "\f(CW$3\fR is the same as \f(CWsubstr($var, $\-[3], $+[3] \- $\-[3])\fR" 5
.IX Item "$3 is the same as substr($var, $-[3], $+[3] - $-[3])"
.RE
.RS 8
.RE
.IP "%\-" 8
.IX Xref "%-"
.PD
Similar to \f(CW\*(C`%+\*(C'\fR, this variable allows access to the named capture buffers
in the last successful match in the currently active dynamic scope. To
each capture buffer name found in the regular expression, it associates a
reference to an array containing the list of values captured by all
buffers with that name (should there be several of them), in the order
where they appear.
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Here's an example:
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.Vb 10
\&    if (\*(Aq1234\*(Aq =~ /(?<A>1)(?<B>2)(?<A>3)(?<B>4)/) {
\&        foreach my $bufname (sort keys %\-) {
\&            my $ary = $\-{$bufname};
\&            foreach my $idx (0..$#$ary) {
\&                print "\e$\-{$bufname}[$idx] : ",
\&                      (defined($ary\->[$idx]) ? "\*(Aq$ary\->[$idx]\*(Aq" : "undef"),
\&                      "\en";
\&            }
\&        }
\&    }
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would print out:
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.Vb 4
\&    $\-{A}[0] : \*(Aq1\*(Aq
\&    $\-{A}[1] : \*(Aq3\*(Aq
\&    $\-{B}[0] : \*(Aq2\*(Aq
\&    $\-{B}[1] : \*(Aq4\*(Aq
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The keys of the \f(CW\*(C`%\-\*(C'\fR hash correspond to all buffer names found in
the regular expression.
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The behaviour of \f(CW\*(C`%\-\*(C'\fR is implemented via the
Tie::Hash::NamedCapture module.
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\&\fBNote:\fR \f(CW\*(C`%\-\*(C'\fR and \f(CW\*(C`%+\*(C'\fR are tied views into a common internal hash
associated with the last successful regular expression. Therefore mixing
iterative access to them via \f(CW\*(C`each\*(C'\fR may have unpredictable results.
Likewise, if the last successful match changes, then the results may be
surprising.
.IP "\s-1HANDLE\-\s0>format_name(\s-1EXPR\s0)" 8
.IX Item "HANDLE->format_name(EXPR)"
.PD 0
.ie n .IP "$FORMAT_NAME" 8
.el .IP "\f(CW$FORMAT_NAME\fR" 8
.IX Item "$FORMAT_NAME"
.IP "$~" 8
.IX Xref "$~ $FORMAT_NAME"
.PD
The name of the current report format for the currently selected output
channel.  Default is the name of the filehandle.  (Mnemonic: brother to
\&\f(CW$^\fR.)
.IP "\s-1HANDLE\-\s0>format_top_name(\s-1EXPR\s0)" 8
.IX Item "HANDLE->format_top_name(EXPR)"
.PD 0
.ie n .IP "$FORMAT_TOP_NAME" 8
.el .IP "\f(CW$FORMAT_TOP_NAME\fR" 8
.IX Item "$FORMAT_TOP_NAME"
.IP "$^" 8
.IX Xref "$^ $FORMAT_TOP_NAME"
.PD
The name of the current top-of-page format for the currently selected
output channel.  Default is the name of the filehandle with _TOP
appended.  (Mnemonic: points to top of page.)
.IP "IO::Handle\->format_line_break_characters \s-1EXPR\s0" 8
.IX Item "IO::Handle->format_line_break_characters EXPR"
.PD 0
.ie n .IP "$FORMAT_LINE_BREAK_CHARACTERS" 8
.el .IP "\f(CW$FORMAT_LINE_BREAK_CHARACTERS\fR" 8
.IX Item "$FORMAT_LINE_BREAK_CHARACTERS"
.ie n .IP "$:" 8
.el .IP "\f(CW$:\fR" 8
.IX Xref "$: FORMAT_LINE_BREAK_CHARACTERS"
.IX Item "$:"
.PD
The current set of characters after which a string may be broken to
fill continuation fields (starting with ^) in a format.  Default is
\&\*(L"\ \en\-\*(R", to break on whitespace or hyphens.  (Mnemonic: a \*(L"colon\*(R" in
poetry is a part of a line.)
.IP "IO::Handle\->format_formfeed \s-1EXPR\s0" 8
.IX Item "IO::Handle->format_formfeed EXPR"
.PD 0
.ie n .IP "$FORMAT_FORMFEED" 8
.el .IP "\f(CW$FORMAT_FORMFEED\fR" 8
.IX Item "$FORMAT_FORMFEED"
.IP "$^L" 8
.IX Xref "$^L $FORMAT_FORMFEED"
.IX Item "$^L"
.PD
What formats output as a form feed.  Default is \ef.
.ie n .IP "$ACCUMULATOR" 8
.el .IP "\f(CW$ACCUMULATOR\fR" 8
.IX Item "$ACCUMULATOR"
.PD 0
.IP "$^A" 8
.IX Xref "$^A $ACCUMULATOR"
.IX Item "$^A"
.PD
The current value of the \fIwrite()\fR accumulator for \fIformat()\fR lines.  A format
contains \fIformline()\fR calls that put their result into \f(CW$^A\fR.  After
calling its format, \fIwrite()\fR prints out the contents of \f(CW$^A\fR and empties.
So you never really see the contents of \f(CW$^A\fR unless you call
\&\fIformline()\fR yourself and then look at it.  See perlform and
\&\*(L"\fIformline()\fR\*(R" in perlfunc.
.ie n .IP "$CHILD_ERROR" 8
.el .IP "\f(CW$CHILD_ERROR\fR" 8
.IX Item "$CHILD_ERROR"
.PD 0
.IP "$?" 8
.IX Xref "$? $CHILD_ERROR"
.PD
The status returned by the last pipe close, backtick (\f(CW\*(C`\`\`\*(C'\fR) command,
successful call to \fIwait()\fR or \fIwaitpid()\fR, or from the \fIsystem()\fR
operator.  This is just the 16\-bit status word returned by the
traditional Unix \fIwait()\fR system call (or else is made up to look like it).  Thus, the
exit value of the subprocess is really (\f(CW\*(C`$? >> 8\*(C'\fR), and
\&\f(CW\*(C`$? & 127\*(C'\fR gives which signal, if any, the process died from, and
\&\f(CW\*(C`$? & 128\*(C'\fR reports whether there was a core dump.  (Mnemonic:
similar to \fBsh\fR and \fBksh\fR.)
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Additionally, if the \f(CW\*(C`h_errno\*(C'\fR variable is supported in C, its value
is returned via $? if any \f(CW\*(C`gethost*()\*(C'\fR function fails.
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If you have installed a signal handler for \f(CW\*(C`SIGCHLD\*(C'\fR, the
value of \f(CW$?\fR will usually be wrong outside that handler.
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Inside an \f(CW\*(C`END\*(C'\fR subroutine \f(CW$?\fR contains the value that is going to be
given to \f(CW\*(C`exit()\*(C'\fR.  You can modify \f(CW$?\fR in an \f(CW\*(C`END\*(C'\fR subroutine to
change the exit status of your program.  For example:
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.Vb 3
\&    END {
\&        $? = 1 if $? == 255;  # die would make it 255
\&    }
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Under \s-1VMS\s0, the pragma \f(CW\*(C`use vmsish \*(Aqstatus\*(Aq\*(C'\fR makes \f(CW$?\fR reflect the
actual \s-1VMS\s0 exit status, instead of the default emulation of \s-1POSIX\s0
status; see \*(L"$?\*(R" in perlvms for details.
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Also see \*(L"Error Indicators\*(R".
.IP "${^CHILD_ERROR_NATIVE}" 8
.IX Xref "$^CHILD_ERROR_NATIVE"
.IX Item "${^CHILD_ERROR_NATIVE}"
The native status returned by the last pipe close, backtick (\f(CW\*(C`\`\`\*(C'\fR)
command, successful call to \fIwait()\fR or \fIwaitpid()\fR, or from the \fIsystem()\fR
operator.  On POSIX-like systems this value can be decoded with the
\&\s-1WIFEXITED\s0, \s-1WEXITSTATUS\s0, \s-1WIFSIGNALED\s0, \s-1WTERMSIG\s0, \s-1WIFSTOPPED\s0, \s-1WSTOPSIG\s0
and \s-1WIFCONTINUED\s0 functions provided by the \s-1POSIX\s0 module.
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Under \s-1VMS\s0 this reflects the actual \s-1VMS\s0 exit status; i.e. it is the same
as $? when the pragma \f(CW\*(C`use vmsish \*(Aqstatus\*(Aq\*(C'\fR is in effect.
.IP "${^ENCODING}" 8
.IX Xref "$^ENCODING"
.IX Item "${^ENCODING}"
The \fIobject reference\fR to the Encode object that is used to convert
the source code to Unicode.  Thanks to this variable your perl script
does not have to be written in \s-1UTF\-8\s0.  Default is \fIundef\fR.  The direct
manipulation of this variable is highly discouraged.
.ie n .IP "$OS_ERROR" 8
.el .IP "\f(CW$OS_ERROR\fR" 8
.IX Item "$OS_ERROR"
.PD 0
.ie n .IP "$ERRNO" 8
.el .IP "\f(CW$ERRNO\fR" 8
.IX Item "$ERRNO"
.IP "$!" 8
.IX Xref "$! $ERRNO $OS_ERROR"
.PD
If used numerically, yields the current value of the C \f(CW\*(C`errno\*(C'\fR
variable, or in other words, if a system or library call fails, it
sets this variable.  This means that the value of \f(CW$!\fR is meaningful
only \fIimmediately\fR after a \fBfailure\fR:
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.Vb 10
\&    if (open(FH, $filename)) {
\&        # Here $! is meaningless.
\&        ...
\&    } else {
\&        # ONLY here is $! meaningful.
\&        ...
\&        # Already here $! might be meaningless.
\&    }
\&    # Since here we might have either success or failure,
\&    # here $! is meaningless.
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In the above \fImeaningless\fR stands for anything: zero, non-zero,
\&\f(CW\*(C`undef\*(C'\fR.  A successful system or library call does \fBnot\fR set
the variable to zero.
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If used as a string, yields the corresponding system error string.
You can assign a number to \f(CW$!\fR to set \fIerrno\fR if, for instance,
you want \f(CW"$!"\fR to return the string for error \fIn\fR, or you want
to set the exit value for the \fIdie()\fR operator.  (Mnemonic: What just
went bang?)
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Also see \*(L"Error Indicators\*(R".
.ie n .IP "%OS_ERROR" 8
.el .IP "\f(CW%OS_ERROR\fR" 8
.IX Item "%OS_ERROR"
.PD 0
.ie n .IP "%ERRNO" 8
.el .IP "\f(CW%ERRNO\fR" 8
.IX Item "%ERRNO"
.IP "%!" 8
.IX Xref "%!"
.PD
Each element of \f(CW\*(C`%!\*(C'\fR has a true value only if \f(CW$!\fR is set to that
value.  For example, \f(CW$!{ENOENT}\fR is true if and only if the current
value of \f(CW$!\fR is \f(CW\*(C`ENOENT\*(C'\fR; that is, if the most recent error was
\&\*(L"No such file or directory\*(R" (or its moral equivalent: not all operating
systems give that exact error, and certainly not all languages).
To check if a particular key is meaningful on your system, use
\&\f(CW\*(C`exists $!{the_key}\*(C'\fR; for a list of legal keys, use \f(CW\*(C`keys %!\*(C'\fR.
See Errno for more information, and also see above for the
validity of \f(CW$!\fR.
.ie n .IP "$EXTENDED_OS_ERROR" 8
.el .IP "\f(CW$EXTENDED_OS_ERROR\fR" 8
.IX Item "$EXTENDED_OS_ERROR"
.PD 0
.IP "$^E" 8
.IX Xref "$^E $EXTENDED_OS_ERROR"
.IX Item "$^E"
.PD
Error information specific to the current operating system.  At
the moment, this differs from \f(CW$!\fR under only \s-1VMS\s0, \s-1OS/2\s0, and Win32
(and for MacPerl).  On all other platforms, \f(CW$^E\fR is always just
the same as \f(CW$!\fR.