I am probably more familiar than most with the exact code you're talking about ;)

Anyway, I ported/adapted CGI::Application to PHP for a project I was working on and I came to a similar conclusion as others in this thread, but I'll try to explain it a little more clearly.

First I have CGI::Application. I subclassed that with something like: MyApplication

From there, I have 3 different areas that require different levels of authentication.

1: public (no auth)
2: registered users (auth against users table or something)
3: administrators (auth against users table + admin table or something)

So I have three different "base" classes that all my regular CGI::Applications inherit from.

MyApplication::Public
MyApplication::Registered
MyApplication::Admin

Each of these classes have inside them the prerun modes required to authenticate the user. If the prerun mode can't authenticate, it bumps them to the login page. After login is successful, it forwards them back to page they originally tried to access.

Then, all my various CGI::Application modules inherit from one of those 3 modules. The added benefit is that it's really easy to see at a glance what type of permission a user needs to access run modes in a specific module.