HTML::Mason Perl module

 Mason allows web pages and sites to be constructed from shared,
 reusable building blocks called components. Components contain a mix
 of Perl and HTML, and can call each other and pass values back and
 forth like subroutines. Components increase modularity and eliminate
 repetitive work: common design elements (headers, footers, menus,
 logos) can be extracted into their own components where they need be
 changed only once to affect the whole site.
 .
 Other Mason features include a graphical site previewing utility, an
 HTML/data caching model, and the ability to walk through requests with
 the Perl debugger.