eating cucumbers without permission...

It’s generally less useful than piping requests through a dispatcher file, but you can use Apache actions to pass all files with a certain extension (or MIME type) through a script of your choosing. If you fill a site with .text text files in [Markdown][m] syntax, for example, you can do something like this:

AddHandler markdown .text
Action markdown /markup.cgi

Or this:

AddType text/prs.markdown .text
Action text/prs.markdown /markup.cgi

Every .text file will be passed to markup.cgi, which will add headers, footers, and process the text into HTML.

Since that’s of little use to most people — though I use it quite satisfactorily — I’ll move on to something far more common: automagic syntax colouring for script source files.