Rather than write your own templating system, I think it would serve you better to look at the other options like HTML::Template and Template Toolkit. If you prefer in-line perl code, Mason is a good option. Nearly all of the perl templating systems compile the template to normal perl code, so there's nothing really unique that I can see about Pas.
There are also nice systems built on top of some of these, like OpenInteract and Apache::PageKit.