There are a number of application engines that use mod_perl as their foundation but provide application frameworks in their own right.

HTML::Embperl

A tool for embedding Perl in HTML

HTML::Mason

Also embeds Perl in HTML but additionally provides an elaborate component based content management and publishing system.

Apache::ASP

Enables ASP development, including ASP sessions, in Perl on Apache. Visual Basic fans will be out of luck here though.

Using these and server embedded logic with PerlHandler's we can achieve a great deal of performance, flexibility and scalability with Apache.