http://perl.apache.org/docs/tutorials/tmpl/comparison/comparison.html

specifically the following:

Introduction

Go on, admit it: you’ve written a templating system. It’s okay, nearly everyone has at some point. You start out with something beautifully simple like

$HTML =~ s/\$(\w+)/${$1}/g

and end up adding conditionals and loops and includes until you’ve created your very own unmaintainable monster.

…ummm…

mine actually looks like

$codeblock =~ s/<!--\$(.*?)\$-->/${$1}/eg;

just close enough to be depressing.