"A comprehensive address verification system" does not take a few hours to make. In another comment on this thread I posted a link to an amazingly detailed address format database and I'm quite sure it took longer than that to make.
I think this would be an awesome open source project!
To clarify: I'm not suggesting that this AVS be made from scratch. That definitely would take, as you say, more than a few hours -- not to mention that it's unnecessary.
Finding the rules and data is but a trivial, slightly time-consuming task. I saw your link before posting my previous comment and took this into consideration: someone reading this immediately has a comprehensive DB of address formats.
"A few hours" may have been a bit ambitious, but over a weekend, and with the required data already available, creating a back-end solution to this is surely not out of the realms of possibility for a reasonably competent programmer?