apache-mod_perl incorporates a Perl interpreter into the apache web server,
so that the Apache web server can directly execute Perl code.
Mod_perl links the Perl runtime library into the apache web server and
provides an object-oriented Perl interface for apache's C language
API. The end result is a quicker CGI script turnaround process, since
no external Perl interpreter has to be started.

Install apache-mod_perl if you're installing the apache web server and you'd
like for it to directly incorporate a Perl interpreter.

You can build apache-mod_perl with some conditional build switches;

(ie. use with rpm --rebuild):
--with[out] debug Compile with debugging code (forces --with test)
--with[out] test Initiate a Apache-Test run