Perl

a computer language that is used for text manipulation, esp on the World Wide Web

Perl

[pərl] (computer science) Practical Extraction and Reporting Language

Perl

(language, tool)A high-level programming language, startedby Larry Wall in 1987 and developed as an open sourceproject. It has an eclectic heritage, deriving from theubiquitous C programming language and to a lesser extentfrom sed, awk, various Unix shell languages, Lisp,and at least a dozen other tools and languages. Originallydeveloped for Unix, it is now available for manyplatforms.

Perl's elaborate support for regular expression matching andsubstitution has made it the language of choice for tasksinvolving string manipulation, whether for text or binarydata. It is particularly popular for writing CGI scripts.

The language's highly flexible syntax and concise regularexpression operators, make densely written Perl codeindecipherable to the uninitiated. The syntax is, however,really quite simple and powerful and, once the basics havebeen mastered, a joy to write.

Perl's only primitive data type is the "scalar", which canhold a number, a string, the undefined value, or a typedreference. Perl's aggregate data types are arrays, whichare ordered lists of scalars indexed by natural numbers,and hashes (or "associative arrays") which are unorderedlists of scalars indexed by strings. A reference can point toa scalar, array, hash, function, or filehandle. Objectsare implemented as references "blessed" with a class name.Strings in Perl are eight-bit clean, including nulls, andso can contain binary data.

Unlike C but like most Lisp dialects, Perl internally anddynamically handles all memory allocation, garbage collection, and type coercion.

Perl supports closures, recursive functions, symbolswith either lexical scope or dynamic scope, nested data structures of arbitrary content and complexity (as lists orhashes of references), and packages (which can serve asclasses, optionally inheriting methods from one or moreother classes). There is ongoing work on threads,Unicode, exceptions, and backtracking. Perl programfiles can contain embedded documentation in POD (Plain OldDocumentation), a simple markup language.

The normal Perl distribution contains documentation for thelanguage, as well as over a hundred modules (programlibraries). Hundreds more are available from TheComprehensive Perl Archive Network. Modules are themselvesgenerally written in Perl, but can be implemented asinterfaces to code in other languages, typically compiled C.

The free availability of modules for almost any conceivabletask, as well as the fact that Perl offers direct access toalmost all system calls and places no arbitrary limits ondata structure size or complexity, has led some to describePerl, 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 asthe language of choice of many World-Wide Web developers.CGI interfaces and libraries for Perl exist for severalplatforms and Perl's speed and flexibility make it wellsuited 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 andits common use as a glue language, makes Perl somewhat hard toclassify as either a "scripting language" or an"applications language" -- see Ousterhout's dichotomy.Perl programs are usually called "Perl scripts", if only forhistorical 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 subroutinecalls, and method inheritance.

The spelling "Perl" is preferred over the older "PERL" (eventhough some explain the language's name as originating in theacronym for "Practical Extraction and Report Language"). Theprogram 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, asof 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. ISBN0-93715-64-1].

["Learning Perl" by Randal L. Schwartz, O'Reilly & Associates,Inc., Sebastopol, CA].

Perl

(Practical Extraction Report Language) A programming language written by Larry Wall that combines syntax from several Unix utilities and languages. Introduced in 1987, Perl is designed to handle a variety of system administrator functions and provides comprehensive string handling functions. It is widely used to write Web server programs for such tasks as automatically updating user accounts and newsgroup postings, processing removal requests, synchronizing databases and generating reports. Perl has also been adapted to non-Unix platforms. See mod_perl and LWP. See also PURL.