We use both
HTML::Template and
Template Toolkit at work. We started down the HTML::Template road and moved to Template Toolkit for the added flexibility and compiled template caching it provides. They have somwhat different design strategies from which they approach the templating problem. Find the one that works best for you and your environment.
If you are dead set on mixing your perl and HTML, which I will agree with the other monks is a bad idea, you might look at HTML::Embperl