[mod_perl | http://perl.apache.org/] marries [Perl] to [Apache]. It embeds the [Perl] interpreter in an [Apache] module to make it possible to write request handlers for [Apache] in [Perl], rather than writing them as modules in [C]. Compiled [Perl] code is kept in memory once it is loaded, eliminating the overhead of [CGI] scripts and opening up control over all stages of [Apache]'s request processing rather than just the content generation phase. 

  

 [mod_perl] comes with a variety of stock request handlers. Perhaps its most popular use is for those stock request handlers (Apache::Registry and Apache::!PerlRun, as well as several specific variations thereof) that attempt to offer its benefits to any [Perl] [CGI] script simply by adding a few lines to the [Apache] configuration. No adjustment to the scripts is required, unless they were written in really dirty style. (Note however that rewriting them as true [mod_perl] request handlers still offers better performance at slightly lower memory consumption; this is a question of tradeoffs to be made.)