ch00_01.htm

编程珍珠,里面很多好用的代码,大家可以参考学习呵呵,

point across.  Any level of language proficiency is acceptable in Perl
culture.  We won't send the language police after you.  A Perl script is
"correct" if it gets the job done before your boss fires you.</p>

<p>Though simple in many ways, Perl is also a rich language, and there is
much to learn about it.  That's the price of making hard things
possible.  Although it will take some time for you to absorb all that
Perl can do, you will be glad that you have access to the extensive
capabilities of Perl when the time comes that you need them.</p>

<p>Because of its heritage, Perl was a rich language even when it was
"just" a data-reduction language, designed for navigating files,
scanning large amounts of text, creating and obtaining dynamic data, and
printing easily formatted reports based on that data.  But somewhere
along the line, Perl started to blossom.  It also became a language for
filesystem manipulation, process management, database administration,
client-server programming, secure programming, web-based information
management, and even for object-oriented and functional programming.
These capabilities were not just slapped onto the side of Perl--each new
capability works synergistically with the others because Perl was
designed to be a glue language from the start.</p>

<p>
<a name="INDEX-2"></a>
But Perl can glue together more than its own features.  Perl is designed
to be modularly extensible.  Perl allows you to rapidly design, program,
debug, and deploy applications, and it also allows you to easily extend
the functionality of these applications as the need arises.  You can
embed Perl in other languages, and you can embed other languages in
Perl.  Through the module importation mechanism, you can use these
external definitions as if they were built-in features of Perl.
Object-oriented external libraries retain their object-orientedness in
Perl.</p>

<p>
<a name="INDEX-3"></a>
Perl helps you in other ways, too.  Unlike strictly interpreted
languages such as command files or shell scripts, which compile and
execute a program one command at a time, Perl first compiles your whole
program quickly into an intermediate format.  Like any other compiler,
it performs various optimizations and gives you instant feedback on
everything from syntax and semantic errors to library binding mishaps.
Once Perl's compiler frontend is happy with your program, it passes off
the intermediate code to the interpreter to execute (or optionally to
any of several modular back ends that can emit C or bytecode).  This
all sounds complicated, but the compiler and interpreter are quite
efficient, and most of us find that the typical compile-run-fix cycle
is measured in mere seconds.  Together with Perl's many fail-soft
characteristics, this quick turnaround capability makes Perl a language
in which you really can do rapid prototyping.  Then later, as your
program matures, you can tighten the screws on yourself and make
yourself program with less flair but more discipline.  Perl helps you
with that, too, if you ask nicely.</p>

<p>
<a name="INDEX-4"></a>
Perl also helps you to write programs more securely.  In addition to
all the typical security interfaces provided by other languages,
Perl also guards against accidental security errors through a unique
data-tracing mechanism that automatically determines which data came
from insecure sources and prevents dangerous operations before they can
happen.  Finally, Perl lets you set up specially protected compartments
in which you can safely execute Perl code of dubious origin, disallowing
dangerous operations.</p>

<p>But, paradoxically, the way in which Perl helps you the most has almost
nothing to do with Perl and everything to do with the people who use
Perl.  Perl folks are, frankly, some of the most helpful folks on
earth.  If there's a religious quality to the Perl movement, then this
is at the heart of it.  Larry wanted the Perl community to function
like a little bit of heaven, and by and large he seems to have gotten
his wish, so far.  Please do your part to keep it that way.</p>

<p>Whether you are learning Perl because you want to save the world, or
just because you are curious, or because your boss told you to, this
handbook will lead you through both the basics and the intricacies.  And
although we don't intend to teach you how to program, the perceptive
reader will pick up some of the art, and a little of the science, of
programming.  We will encourage you to develop the three great virtues of
a programmer: <em class="emphasis">laziness</em>, <em class="emphasis">impatience</em>, and <em class="emphasis">hubris</em>.  Along the
way, we hope you find the book mildly amusing in some spots (and wildly
amusing in others).  And if none of this is enough to keep you awake,
just keep reminding yourself that learning Perl will increase the value
of your resume.  So keep reading.</p>



















































































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