Hm... possibly you should consider using Mason then... one of Mason's strengths is that Mason templates tend to have the feel of HTML, which lets web-designer types feel like they know what's going on. Hypothetically a perl programmer might be inclined to slip in a lot of perl into the template, but in practice it's just as easy to put it in a perl module, and just add just enough glue code into the template to get it to use the module.

Myself, I'm less familiar with Template Toolkit, but I would say if you have a choice of ways to do it, you probably want to use either Mason or Template Toolkit: those are the two competing schools at the moment (notably they both have O'Reilley books), and in effect they're defacto standards.