[plt-scheme] Okay, this is ugly

> That was actually my first thought, but I didn't think I could call
> env-get-binding in the failure thunk of hash-table-get.

Why did you think that?

Your concern about static vs dynamic scope is, a bit like the
first version of the code you sent, overthinking the problem and thus
getting you into a muddle.  Just write the interpreter and write test
cases to see whether or not you got the scoping right.  If you didn't,
go back and try to examine where it failed; if you think you did, then
try to understand why it worked.

Shriram