Perl
Perl is a high-level, general-purpose, interpreted, dynamic programming language.
Though Perl is not officially an acronym, there are various backronyms in use, such as: Practical Extraction and Reporting Language, and (more whimsicallly) Pathologically Eclectic Rubbish Lister. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. In the 1990s it became very popular for web scripting, though other languages have gained more popularity for this purpose lately.
It is one of the possibilities for the P in LAMP (a set of technologies used in many web back-ends, including Linux, Apache, and MySQL, notable for being free, open-source software in contrast to proprietary technologies such as those from Microsoft) along with PHP and Python.
The book Programming Perl by Larry Wall and Randal L. Schwartz (and other co-authors in later editions), ISBN 978-0-596-00492-7 or ISBN 978-1-4493-9890-3 for the e-book version, is regarded as the definitive reference for the language, and is usually referred to as "the camel book" because of the picture of a camel on the cover (in keeping with publisher O'Reilley's use of animals on its technical book covers).
Programs in Perl are usually stored in plain-text files, to be run by the Perl interpreter.
Perl 6 has been under development for years, with a number of differences from earlier versions of Perl which make programs incompatible both forward and reverse. This new version uses a virtual machine called "Parrot" with a language that is intermediate between Perl and native machine code.
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Extension convention
.pl
Command line script. Used for main Perl programs to be executed, which might in turn pull in modules or headers of other extensions. Sometimes used for CGI-executed scripts as well as command-line-executed ones, although other extensions exist for CGI as shown below.
.pm
Perl Module (library). A set of Perl code (usually object-oriented) designed to be used by programs. A wide range of libraries are available in an open-source manner through resource sites such as CPAN, or developers may create their own libraries as part of the structure of the systems they are developing.
.ph
Perl Header (file inserted within script/program). Sometimes used for pieces of code, such as initialization of variables for configuration purposes, that is embedded in a Perl program, similarly to the use of .h in C. Not used as often in Perl as in other languages.
.cgi
Common Gateway Interface usage (server side scripting on webservers / webservices). This use is ambiguous, since many other languages are used in CGI scripting, and might show up with a .cgi extension as well.
.fcgi
API independent Common Gateway Interface usage (server side scripting on webservers / webservices).
Resources
- CPAN: source of Perl modules and libraries
- CPANTS: CPAN Testing Service
- FastCGI.com
