I can't recommend a templating system enough. I wrote dynamic Web sites with HERE docs for a couple of years and then switched to HTML::Template. Keeping the server-side separate from the client-side is huge in my graphic design firm where I have people doing HTML, but don't know a lick of Perl.

The next huge advance for me was switching to CGI::Application, a framework that makes working with dynamic Web sites and templating systems so much easier (lots of great plugins).