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