Mason is a powerful Perl-based web site development and delivery engine. With Mason you can embed Perl code in your HTML and construct pages from shared, reusable components.

Mason solves the common problems of site development: caching, debugging, templating, maintaining development and production sites, and more.

Mason is 100% free and open source. Although it can be used from CGI or even stand-alone, it is optimally designed for use with two other open source technologies: mod_perl and Apache.

Source: Mason