mod_perl is an Apache extension written by Doug MacEachern for embedding the Perl interpreter in Apache Web server. It integrates the power of Perl with the stability of the Apache Web server and provides Web applications with high performance. As the interpreter is embedded in the Web server, the startup and compilation time for any HTTP request comprising a Perl script is reduced. All the scripts and the modules can be compiled once when the server is started and rerun many times when the requests come.
mod_perl provides full access to the Web server and enables intervening and customizing the various phases of HTTP request processing like:
URL to filename translation
Authorization
Response Generation
Logging