(PE-5860) Add regex support to wrap-proxy

This PR adds regular expression support to the wrap-proxy function.
No big deal, but typically function arguments are aligned, so this `http-opts` hiding down here took me a bit to see.

Also, it's difficult to see where the true branch ends the false branch begins since the `let` block is so big.  I would extract this out into another function for readability.

Actually, I might just consider making this entire anonymous `(fn [req...` function a top-level function.  Either way, I think pulling some of this code out into another function would help.