My only experience here is with some older versions of IMP. Granted that's PHP not Perl, but the same basic issues apply of how do you package a web application for easy installation. They did it the first way you suggest. The steps were 1) unpack the distribution into a directory on your web root 2) acccess the site from localhost and fill in the form they give you 3) let the script triggered by that form create all the config files, copy stuff to the appropriate place, etc.

OTOH, IMP subsequently abandoned that approach and now the installation consists of unpacking, running a script on the console that prompts you for the relevant questions, and further editing config files manually as needed.