Did you have a look at Text::Template and HTML::Template? I don't know HTML::Template that well, but I know Text::Template and it does what you describe, and more, in a much more robust and powerful way. It is also just as easy to use.

I definitely would _not_ re-invent an ad-hoc templating system when people like Dominus have already written it, and when it has been used for several years by thousands of users.