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.