I'm surprised nobody mentioned HTML::Template. This is another way to do it that many also like.

Also, here are some interesting and related PM discussions:

Ways to Seperate Code from Content

Design vs. Code vs. Maintenance, wide ranging thread

CGI Help Guide, just in case;

Content management system recommendations?, YAWTAI (Yet Another Way to Ask it), long thread including bits about other CMS's.

All of these are Recommended Reading, and there's more to be found in Super Search I'm sure.

Hope these help.