I used to be in that camp too. Nowadays I don't confine myself though unless there is no pure-Perl module for the purpose. The reason is simple: any Perl code can be placed where a CGI script can, so any pure-Perl modules can be passed along with the script - even if I have to download the modules and copypaste the code into the file myself.

Care needs to be taken that all the imports work correctly of course, but it's far from impossible. I'm thinking some sort of packaging mechanism based on Coderefs in @INC (was: Building a Simple Perl Module Database) could actually make the whole thing totally transparent.

Makeshifts last the longest.