Preferential Voting - how does it work?

I finally get it. It only took 16 years, but I've finally spent the
necessary 10 minutes to understand it. A bit sad really.

http://www.abc.net.au/elections/federal/2004/guide/howpreferenceswork.htm

And also found a Ruby implementation of Preferential voting, along
with other systems.

http://rubyvote.rubyforge.org/