Perl 音标拼音: [p'ɚl]
A {high -level } programming language , started
by {Larry Wall } in 1987 and developed as an {open source }
project . It has an eclectic heritage , deriving from the
ubiquitous {C } programming language and to a lesser extent
from {sed }, {awk }, various {Unix } {shell } languages , {Lisp },
and at least a dozen other tools and languages . Originally
developed for {Unix }, it is now available for many
platforms }.
Perl 's elaborate support for {regular expression } matching and
substitution has made it the {language of choice } for tasks
involving {string manipulation }, whether for text or binary
data . It is particularly popular for writing {CGI scripts }.
The language 's highly flexible syntax and concise regular
expression operators , make densely written Perl code
indecipherable to the uninitiated . The syntax is , however ,
really quite simple and powerful and , once the basics have
been mastered , a joy to write .
Perl 's only {primitive } data type is the "scalar ", which can
hold a number , a string , the undefined value , or a typed
reference . Perl 's {aggregate } data types are {arrays }, which
are ordered lists of {scalars } indexed by {natural numbers },
and hashes (or "{associative arrays }") which are unordered
lists of scalars indexed by strings . A reference can point to
a scalar , array , hash , {function }, or {filehandle }. {Objects }
are implemented as references "{blessed }" with a {class } name .
Strings in Perl are {eight -bit clean }, including {nulls }, and
so can contain {binary data }.
Unlike C but like most Lisp dialects , Perl internally and
dynamically handles all memory allocation , {garbage
collection }, and type {coercion }.
Perl supports {closures }, {recursive functions }, {symbols }
with either {lexical scope } or {dynamic scope }, nested {data
structures } of arbitrary content and complexity (as lists or
hashes of references ), and packages (which can serve as
classes , optionally inheriting {methods } from one or more
other classes ). There is ongoing work on {threads },
Unicode }, {exceptions }, and {backtracking }. Perl program
files can contain embedded documentation in {POD } (Plain Old
Documentation ), a simple markup language .
The normal Perl distribution contains documentation for the
language , as well as over a hundred modules (program
libraries ). Hundreds more are available from The
Comprehensive Perl Archive Network }. Modules are themselves
generally written in Perl , but can be implemented as
interfaces to code in other languages , typically compiled C .
The free availability of modules for almost any conceivable
task , as well as the fact that Perl offers direct access to
almost all {system calls } and places no arbitrary limits on
data structure size or complexity , has led some to describe
Perl , in a parody of a famous remark about {lex }, as the
Swiss Army chainsaw " of programming .
The use of Perl has grown significantly since its adoption as
the language of choice of many {World -Wide Web } developers .
CGI } interfaces and libraries for Perl exist for several
platforms } and Perl 's speed and flexibility make it well
suited for form processing and on -the -fly {web page } creation .
Perl programs are generally stored as {text } {source } files ,
which are compiled into {virtual machine } code at run time ;
this , in combination with its rich variety of data types and
its common use as a glue language , makes Perl somewhat hard to
classify as either a "{scripting language }" or an
applications language }" -- see {Ousterhout 's dichotomy }.
Perl programs are usually called "Perl scripts ", if only for
historical reasons .
Version 5 was a major rewrite and enhancement of version 4 ,
released sometime before November 1993 . It added real {data
structures } by way of "references ", un -adorned {subroutine }
calls , and {method } {inheritance }.
The spelling "Perl " is preferred over the older "PERL " (even
though some explain the language 's name as originating in the
acronym for "Practical Extraction and Report Language "). The
program that interprets /compiles Perl code is called
perl ", typically "/usr /local /bin /perl " or "/usr /bin /perl ".
Latest version : 5 .005_03 stable , 5 .005_62 in development , as
of 1999 -12 -04 .
http ://perl .com /)}.
Usenet } newsgroups : {news :comp .lang .perl .announce },
news :comp .lang .perl .misc }.
Programming Perl ", Larry Wall and Randal L . Schwartz ,
O 'Reilly & Associates, Inc. Sebastopol, CA. ISBN
Practical Extraction and Report Language (
PERL )
Perl : /
perl /,
n . [
Practical Extraction and Report Language ,
a .
k .
a .
Pathologically Eclectic Rubbish Lister ]
An interpreted language developed by Larry Wall ,
author of patch (
1 )
and rn (
1 )).
Superficially resembles awk ,
but is much hairier ,
including many facilities reminiscent of sed (
1 )
and shells and a comprehensive Unix system -
call interface .
Unix sysadmins ,
who are almost always incorrigible hackers ,
generally consider it one of the languages of choice ,
and it is by far the most widely used tool for making ‘
live ’
web pages via CGI .
Perl has been described ,
in a parody of a famous remark about lex (
1 ),
as the Swiss -
Army chainsaw of Unix programming .
Though Perl is very useful ,
it would be a stretch to describe it as pretty or elegant ;
people who like clean ,
spare design generally prefer Python .
See also Camel Book ,
TMTOWTDI .
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