I got the validation system working. As a reward, I'm going to watch the rest of Monk before I go over and comb through the code for any extra refactoring that could happen.
Oh, and in response to chromatic's earlier comment about test-writing making later refactoring easier: I'll remember that. This really wasn't supposed to be a 700-line script, or I'd have been more systematic.
Now that I think of it, perhaps a rule of thumb would be good here: Anything over twenty lines or so, start writing tests, because I will need them.