This is a really cool example, and I don't want to lose it. However, I'm reasonably sure that there's easier ways to do this, and I'm not yet sure that the example given actually works. Need to revisit this soon.
Removes an inscrutable recipe - I don't know what problem it's trying to solve, and the solution appears to be a completely useless use of RewriteMap to solve a trivial problem that could be better done with Alias. Am I missing something?