"Sometimes, a module just isn't logical. For example, when you want to use an external configuration file... This is where do comes in."

Part of what he wants to do sounds like including a table definition, which would be config, not code.

Incidently, there are a number of things which are far less painful to do in Perl than PHP. For instance, sorts of nested structures, or regex. Anything involving a lot of data processing is much faster to code in Perl. I generally use PHP for less complicated functions, and Perl for admin stuff.