Very very nice tutorial ! I was looking for something like this
I was actually thinking of writing something similar with WWW::Selenium
using Greasemonkey+Firefox+some_http_server_running_perl from "scratch"
but now I'm more confident of WWW::Selenium s powers
I have tried Selenium myself,installed it on my computer,it takes a pretty big hit on the resources as I remember...it was written in Java I think,it opened up it's own http server and had installed a firefox extension on my firefox.
Basically the same thing can be done with Greasemonkey since it allows one to write code exactly after the page is rendered.