Perl is a programming language created in 1987 by Larry Wall. Initially designed to efficiently process text, its name is an acronym for Practical Extraction and Report Language.
Fast and flexible
Perl is an interpreted language, compiled at runtinme, which allows for rapid development through unrivalled flexibility. Its motto, "There Is More Than One Way To Do It" (TIMTOWTDI) partly means it doesn't force the programmer into a particular coding style or programming paradigm. It was first in the dynamic interpreted languages arena (ASP, PHP, Ruby, Python, etc.), but never stopped to evolve and improve to keep the lead.
Free and reliable
Perl's source code is totally free, and licensed both under the GNU GPL and the Artistic License. Tens of thousands of unit and functional tests garantee the codebase quality. Systematic use of such procedures allowed Perl to be confirmed as having one of the lowest defect rate per line of code in the open source world. Moreover, portability is a major concern in its development: it runs on more than 80 platforms.
Ready for anything
One of Perl's greatest strengths lies in the plethora of libraries available. They cover nearly every need a programmer could possibly have: database interfaces, network streams and protocols, code testing and QA, security, cryptography, authentication, parsing, graphics manipulation and generation, GUIs, support for all common file formats, e-mail processing and generation, operating system integration, driving of other languages, formal and precision mathematics, natural language processing, bioinformatics, etc. This ubiquity earned Perl a reputation for being the "duct tape of the Internet".
Perl could be branded "a Swiss Army knife" for the UNIX world. Its many libraries make it invaluable to the sysadmin and programmer. The syntax, being in some ways close to C, the shell or awk, make it easy to get a grasp of. It never stopped evolving at a quick pace for 20 years, thanks to the efforts of a tightly knit community of highly knowledgable and technically skilled experts. However it is not as much publicised now, but only because it has reached such a level of maturity that it's taken for granted and not advertised anymore, just like C. Always there, seldom visible. An ancestor for all dynamic languages, Perl is still a consistent choice, as efficient for rapid prototyping as for high-quality production.