>>346
I've written something a little more similar to 4chan's, but I think its close enough. You can copy the relevant code from https://github.com/marlencrabapple/Glaukaba, but I'm not sure if you can just drop it in and have it work. Also, the entire script is pretty much a mess since I started messing with this thing a whole year before I knew what I was doing.

The guys at bunbunmaru (http://bunbunmaru.com/wakaba/general/wakaba.pl?task=cata) made one that may be a little more your speed, and if they're willing to share the code then you should be set.

If neither of those work for you, you can try bothering the guy from http://sovietrussia.org/ since I think he also had a catalog mode in his Wakaba installation.