perl590delta.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.

.PP
is merely equivalent to
.PP
.Vb 1
\&   defined $a ? $a : $b
.Ve
.PP
and
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.Vb 1
\&   $c //= $d;
.Ve
.PP
can be used instead of
.PP
.Vb 1
\&   $c = $d unless defined $c;
.Ve
.PP
This operator has the same precedence and associativity as \f(CW\*(C`||\*(C'\fR.
It has a low-precedence counterpart, \f(CW\*(C`err\*(C'\fR, which has the same precedence
and associativity as \f(CW\*(C`or\*(C'\fR.  Special care has been taken to ensure that
those operators 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 "\s-1UTF\-8\s0 no longer default under \s-1UTF\-8\s0 locales"
.IX Subsection "UTF-8 no longer default under UTF-8 locales"
In Perl 5.8.0 many Unicode features were introduced.   One of them
was found to be of more nuisance than benefit: the automagic
(and silent) \*(L"UTF\-8\-ification\*(R" of filehandles, including the
standard filehandles, if the user's locale settings indicated
use of \s-1UTF\-8\s0.
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For example, if you had \f(CW\*(C`en_US.UTF\-8\*(C'\fR as your locale, your \s-1STDIN\s0 and
\&\s-1STDOUT\s0 were automatically \*(L"\s-1UTF\-8\s0\*(R", in other words an implicit
binmode(..., \*(L":utf8\*(R") was made.  This meant that trying to print, say,
\&\fIchr\fR\|(0xff), ended up printing the bytes 0xc3 0xbf.  Hardly what
you had in mind unless you were aware of this feature of Perl 5.8.0.
The problem is that the vast majority of people weren't: for example
in RedHat releases 8 and 9 the \fBdefault\fR locale setting is \s-1UTF\-8\s0, so
all RedHat users got \s-1UTF\-8\s0 filehandles, whether they wanted it or not.
The pain was intensified by the Unicode implementation of Perl 5.8.0
(still) having nasty bugs, especially related to the use of s/// and
tr///.  (Bugs that have been fixed in 5.8.1)
.PP
Therefore a decision was made to backtrack the feature and change it
from implicit silent default to explicit conscious option.  The new
Perl command line option \f(CW\*(C`\-C\*(C'\fR and its counterpart environment
variable \s-1PERL_UNICODE\s0 can now be used to control how Perl and Unicode
interact at interfaces like I/O and for example the command line
arguments.  See \*(L"\-C\*(R" in perlrun and \*(L"\s-1PERL_UNICODE\s0\*(R" in perlrun for more
information.
.Sh "Unsafe signals again available"
.IX Subsection "Unsafe signals again available"
In Perl 5.8.0 the so-called \*(L"safe signals\*(R" were introduced.  This
means that Perl no longer handles signals immediately but instead
\&\*(L"between opcodes\*(R", when it is safe to do so.  The earlier immediate
handling easily could corrupt the internal state of Perl, resulting
in mysterious crashes.
.PP
However, the new safer model has its problems too.  Because now an
opcode, a basic unit of Perl execution, is never interrupted but
instead let to run to completion, certain operations that can take a
long time now really do take a long time.  For example, certain
network operations have their own blocking and timeout mechanisms, and
being able to interrupt them immediately would be nice.
.PP
Therefore perl 5.8.1 introduced a \*(L"backdoor\*(R" to restore the pre\-5.8.0
(pre\-5.7.3, really) signal behaviour.  Just set the environment variable
\&\s-1PERL_SIGNALS\s0 to \f(CW\*(C`unsafe\*(C'\fR, and the old immediate (and unsafe)
signal handling behaviour returns.  See \*(L"\s-1PERL_SIGNALS\s0\*(R" in perlrun
and \*(L"Deferred Signals (Safe Signals)\*(R" in perlipc.
.PP
In completely unrelated news, you can now use safe signals with
POSIX::SigAction.  See \*(L"POSIX::SigAction\*(R" in \s-1POSIX\s0.
.Sh "Tied Arrays with Negative Array Indices"
.IX Subsection "Tied Arrays with Negative Array Indices"
Formerly, the indices passed to \f(CW\*(C`FETCH\*(C'\fR, \f(CW\*(C`STORE\*(C'\fR, \f(CW\*(C`EXISTS\*(C'\fR, and
\&\f(CW\*(C`DELETE\*(C'\fR methods in tied array class were always non-negative.  If
the actual argument was negative, Perl would call \s-1FETCHSIZE\s0 implicitly
and add the result to the index before passing the result to the tied
array method.  This behaviour is now optional.  If the tied array class
contains a package variable named \f(CW$NEGATIVE_INDICES\fR which is set to
a true value, negative values will be passed to \f(CW\*(C`FETCH\*(C'\fR, \f(CW\*(C`STORE\*(C'\fR,
\&\f(CW\*(C`EXISTS\*(C'\fR, and \f(CW\*(C`DELETE\*(C'\fR unchanged.
.Sh "local ${$x}"
.IX Subsection "local ${$x}"
The syntaxes
.PP
.Vb 3
\&        local ${$x}
\&        local @{$x}
\&        local %{$x}
.Ve
.PP
now do localise variables, given that the \f(CW$x\fR is a valid variable name.
.Sh "Unicode Character Database 4.0.0"
.IX Subsection "Unicode Character Database 4.0.0"
The copy of the Unicode Character Database included in Perl 5.8 has
been updated to 4.0.0 from 3.2.0.  This means for example that the
Unicode character properties are as in Unicode 4.0.0.
.Sh "Miscellaneous Enhancements"
.IX Subsection "Miscellaneous Enhancements"
\&\f(CW\*(C`unpack()\*(C'\fR now defaults to unpacking the \f(CW$_\fR.
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\&\f(CW\*(C`map\*(C'\fR in void context is no longer expensive. \f(CW\*(C`map\*(C'\fR is now context
aware, and will not construct a list if called in void context.
.PP
If a socket gets closed by the server while printing to it, the client
now gets a \s-1SIGPIPE\s0.  While this new feature was not planned, it fell
naturally out of PerlIO changes, and is to be considered an accidental
feature.
.PP
PerlIO::get_layers(\s-1FH\s0) returns the names of the PerlIO layers
active on a filehandle.
.PP
PerlIO::via layers can now have an optional \s-1UTF8\s0 method to
indicate whether the layer wants to \*(L"auto\-:utf8\*(R" the stream.
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\&\fIutf8::is_utf8()\fR has been added as a quick way to test whether
a scalar is encoded internally in \s-1UTF\-8\s0 (Unicode).
.SH "Modules and Pragmata"
.IX Header "Modules and Pragmata"
.Sh "Updated Modules And Pragmata"
.IX Subsection "Updated Modules And Pragmata"
The following modules and pragmata have been updated since Perl 5.8.0:
.IP "base" 4
.IX Item "base"
.PD 0
.IP "B::Bytecode" 4
.IX Item "B::Bytecode"
.PD
In much better shape than it used to be.  Still far from perfect, but
maybe worth a try.
.IP "B::Concise" 4
.IX Item "B::Concise"
.PD 0
.IP "B::Deparse" 4
.IX Item "B::Deparse"
.IP "Benchmark" 4
.IX Item "Benchmark"
.PD
An optional feature, \f(CW\*(C`:hireswallclock\*(C'\fR, now allows for high
resolution wall clock times (uses Time::HiRes).
.IP "ByteLoader" 4
.IX Item "ByteLoader"
See B::Bytecode.
.IP "bytes" 4
.IX Item "bytes"
Now has bytes::substr.
.IP "\s-1CGI\s0" 4
.IX Item "CGI"
.PD 0
.IP "charnames" 4
.IX Item "charnames"
.PD
One can now have custom character name aliases.
.IP "\s-1CPAN\s0" 4
.IX Item "CPAN"
There is now a simple command line frontend to the \s-1CPAN\s0.pm
module called \fIcpan\fR.
.IP "Data::Dumper" 4
.IX Item "Data::Dumper"
A new option, Pair, allows choosing the separator between hash keys
and values.
.IP "DB_File" 4
.IX Item "DB_File"
.PD 0
.IP "Devel::PPPort" 4
.IX Item "Devel::PPPort"
.IP "Digest::MD5" 4
.IX Item "Digest::MD5"
.IP "Encode" 4
.IX Item "Encode"
.PD
Significant updates on the encoding pragma functionality
(tr/// and the \s-1DATA\s0 filehandle, formats).
.Sp
If a filehandle has been marked as to have an encoding, unmappable
characters are detected already during input, not later (when the
corrupted data is being used).
.Sp
The \s-1ISO\s0 8859\-6 conversion table has been corrected (the 0x30..0x39
erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039).  The
\&\s-1GSM\s0 03.38 conversion did not handle escape sequences correctly.  The
\&\s-1UTF\-7\s0 encoding has been added (making Encode feature-complete with
Unicode::String).
.IP "fields" 4
.IX Item "fields"
.PD 0
.IP "libnet" 4
.IX Item "libnet"
.IP "Math::BigInt" 4
.IX Item "Math::BigInt"
.PD
A lot of bugs have been fixed since v1.60, the version included in Perl
v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to
fail for some large values, and the fixes to the handling of bad inputs.
.Sp
Some new features were added, e.g. the \fIbroot()\fR method, you can now pass
parameters to \fIconfig()\fR to change some settings at runtime, and it is now
possible to trap the creation of NaN and infinity.
.Sp
As usual, some optimizations took place and made the math overall a tad
faster. In some cases, quite a lot faster, actually. Especially alternative
libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the
quite clunky routines like \fIfsqrt()\fR and \fIflog()\fR are now much much faster.
.IP "MIME::Base64" 4
.IX Item "MIME::Base64"
.PD 0
.IP "\s-1NEXT\s0" 4
.IX Item "NEXT"
.PD
Diamond inheritance now works.
.IP "Net::Ping" 4
.IX Item "Net::Ping"
.PD 0
.IP "PerlIO::scalar" 4
.IX Item "PerlIO::scalar"
.PD
Reading from non-string scalars (like the special variables, see
perlvar) now works.
.IP "podlators" 4
.IX Item "podlators"
.PD 0
.IP "Pod::LaTeX" 4
.IX Item "Pod::LaTeX"
.IP "PodParsers" 4
.IX Item "PodParsers"
.IP "Pod::Perldoc" 4
.IX Item "Pod::Perldoc"
.PD
Complete rewrite.  As a side-effect, no longer refuses to startup when
run by root.
.IP "Scalar::Util" 4
.IX Item "Scalar::Util"
New utilities: refaddr, isvstring, looks_like_number, set_prototype.
.IP "Storable" 4
.IX Item "Storable"
Can now store code references (via B::Deparse, so not foolproof).
.IP "strict" 4
.IX Item "strict"
Earlier versions of the strict pragma did not check the parameters
implicitly passed to its \*(L"import\*(R" (use) and \*(L"unimport\*(R" (no) routine.
This caused the false idiom such as:
.Sp
.Vb 2
\&        use strict qw(@ISA);
\&        @ISA = qw(Foo);
.Ve
.Sp
This however (probably) raised the false expectation that the strict
refs, vars and subs were being enforced (and that \f(CW@ISA\fR was somehow
\&\*(L"declared\*(R").  But the strict refs, vars, and subs are \fBnot\fR enforced
when using this false idiom.
.Sp
Starting from Perl 5.8.1, the above \fBwill\fR cause an error to be
raised.  This may cause programs which used to execute seemingly
correctly without warnings and errors to fail when run under 5.8.1.
This happens because
.Sp
.Vb 1
\&        use strict qw(@ISA);
.Ve
.Sp
will now fail with the error:
.Sp
.Vb 1
\&        Unknown \*(Aqstrict\*(Aq tag(s) \*(Aq@ISA\*(Aq
.Ve
.Sp
The remedy to this problem is to replace this code with the correct idiom:
.Sp
.Vb 3