A product I use quite a lot is FxCop for .NET. Ignoring the fact that it is for .NET it has some quite nice features.
One feature I like especially (hence my comment here) is that each rule can point to the FxCop website with a discussion on the guideline and a code example that:
- Breaks the rule
- Shows the fix
Perhaps this is something that could be added? Certainly links to perlfaq where relevant. I realise you are citing the PBP book and point people at the pages in there but why not extend it a little more? It may help newer programmers who may not have the book or have the book to hand. It would also allow you to add more rules that are not necessarily from PBP but from other sources of knowledge such as this site.
Just a thought :)