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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Perl
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 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".
<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
0-93715-64-1].
["Learning Perl" by Randal L. Schwartz, O'Reilly & Associates,
Inc., Sebastopol, CA].
[Jargon File]
(1999-12-04)
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