perlfaq1.1

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 "PERLFAQ1 1"
.TH PERLFAQ1 1 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
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.SH "NAME"
perlfaq1 \- General Questions About Perl ($Revision: 10427 $)
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This section of the \s-1FAQ\s0 answers very general, high-level questions
about Perl.
.Sh "What is Perl?"
.IX Subsection "What is Perl?"
Perl is a high-level programming language with an eclectic heritage
written by Larry Wall and a cast of thousands.  It derives from the
ubiquitous C programming language and to a lesser extent from sed,
awk, the Unix shell, and at least a dozen other tools and languages.
Perl's process, file, and text manipulation facilities make it
particularly well-suited for tasks involving quick prototyping, system
utilities, software tools, system management tasks, database access,
graphical programming, networking, and world wide web programming.
These strengths make it especially popular with system administrators
and \s-1CGI\s0 script authors, but mathematicians, geneticists, journalists,
and even managers also use Perl.  Maybe you should, too.
.Sh "Who supports Perl?  Who develops it?  Why is it free?"
.IX Subsection "Who supports Perl?  Who develops it?  Why is it free?"
The original culture of the pre-populist Internet and the deeply-held
beliefs of Perl's author, Larry Wall, gave rise to the free and open
distribution policy of perl.  Perl is supported by its users.  The
core, the standard Perl library, the optional modules, and the
documentation you're reading now were all written by volunteers.  See
the personal note at the end of the \s-1README\s0 file in the perl source
distribution for more details.  See perlhist (new as of 5.005)
for Perl's milestone releases.
.PP
In particular, the core development team (known as the Perl Porters)
are a rag-tag band of highly altruistic individuals committed to
producing better software for free than you could hope to purchase for
money.  You may snoop on pending developments via the archives at
http://www.xray.mpe.mpg.de/mailing\-lists/perl5\-porters/
and http://archive.develooper.com/perl5\[e-mail]/
or the news gateway nntp://nntp.perl.org/perl.perl5.porters or
its web interface at http://nntp.perl.org/group/perl.perl5.porters ,
or read the faq at http://dev.perl.org/perl5/docs/p5p\-faq.html ,
or you can subscribe to the mailing list by sending
perl5\-porters\[e-mail] a subscription request
(an empty message with no subject is fine).
.PP
While the \s-1GNU\s0 project includes Perl in its distributions, there's no
such thing as \*(L"\s-1GNU\s0 Perl\*(R".  Perl is not produced nor maintained by the
Free Software Foundation.  Perl's licensing terms are also more open
than \s-1GNU\s0 software's tend to be.
.PP
You can get commercial support of Perl if you wish, although for most
users the informal support will more than suffice.  See the answer to
\&\*(L"Where can I buy a commercial version of perl?\*(R" for more information.
.Sh "Which version of Perl should I use?"
.IX Subsection "Which version of Perl should I use?"
(contributed by brian d foy)
.PP
There is often a matter of opinion and taste, and there isn't any one
answer that fits anyone.  In general, you want to use either the current
stable release, or the stable release immediately prior to that one.
Currently, those are perl5.10.x and perl5.8.x, respectively.
.PP
Beyond that, you have to consider several things and decide which is best
for you.
.IP "\(bu" 4
If things aren't broken, upgrading perl may break them (or at least issue
new warnings).
.IP "\(bu" 4
The latest versions of perl have more bug fixes.
.IP "\(bu" 4
The Perl community is geared toward supporting the most recent releases,
so you'll have an easier time finding help for those.
.IP "\(bu" 4
Versions prior to perl5.004 had serious security problems with buffer
overflows, and in some cases have \s-1CERT\s0 advisories (for instance,
http://www.cert.org/advisories/CA\-1997\-17.html ).
.IP "\(bu" 4
The latest versions are probably the least deployed and widely tested, so
you may want to wait a few months after their release and see what
problems others have if you are risk averse.
.IP "\(bu" 4
The immediate, previous releases (i.e. perl5.8.x ) are usually maintained
for a while, although not at the same level as the current releases.
.IP "\(bu" 4
No one is actively supporting Perl 4.  Five years ago it was a dead
camel carcass (according to this document).  Now it's barely a skeleton
as its whitewashed bones have fractured or eroded.
.IP "\(bu" 4
There is no Perl 6 release scheduled, but it will be available when 
it's ready.  Stay tuned, but don't worry that you'll have to change 
major versions of Perl; no one is going to take Perl 5 away from you.
.IP "\(bu" 4
There are really two tracks of perl development: a maintenance version
and an experimental version.  The maintenance versions are stable, and
have an even number as the minor release (i.e. perl5.10.x, where 10 is the
minor release).  The experimental versions may include features that
don't make it into the stable versions, and have an odd number as the
minor release (i.e. perl5.9.x, where 9 is the minor release).
.Sh "What are Perl 4, Perl 5, or Perl 6?"
.IX Subsection "What are Perl 4, Perl 5, or Perl 6?"
(contributed by brian d foy)
.PP
In short, Perl 4 is the past, Perl 5 is the present, and Perl 6 is the
future.
.PP
The number after perl (i.e. the 5 after Perl 5) is the major release
of the perl interpreter as well as the version of the language.  Each
major version has significant differences that earlier versions cannot
support.
.PP
The current major release of Perl is Perl 5, and was released in 1994.
It can run scripts from the previous major release, Perl 4 (March 1991),
but has significant differences. It introduced the concept of references,
complex data structures, and modules.  The Perl 5 interpreter was a
complete re-write of the previous perl sources.
.PP
Perl 6 is the next major version of Perl, but it's still in development
in both its syntax and design.  The work started in 2002 and is still
ongoing.  Many of the most interesting features have shown up in the
latest versions of Perl 5, and some Perl 5 modules allow you to use some
Perl 6 syntax in your programs.  You can learn more about Perl 6 at
http://dev.perl.org/perl6/ .