Nice to see you here. I was just casually looking through the txr-libs there and just randomly spotted this, the CSV library, in a let form:

  (fieldrx (regex-compile ;; using a regex object here messes with emacs syntax highlighting
             "([^,\"\']*(\"([^\"]|\\\\\")*\"|\'([^\']|\\\\\')*\'|)[^,\"\']*)+"))

I understand that here using the #/.../ regex literal object didn't look right in your Emacs, so you dynamically compiled from a string literal.

But that now happens each time you call the function.

Lisp has your back here; we can hoist the compilation of the regex to load time using load-time:

  (fieldrx (load-time (regex-compile "...RE...")))

load-time makes a difference in interpreted code, not just compiled files. Even in interpreted code, the regex-compile expression will be evaluated once only and then the cached value used:

  1> (dotimes (i 5) (prinl "hi"))
  "hi"
  "hi"
  "hi"
  "hi"
  "hi"
  nil
  2> (dotimes (i 5) (load-time (prinl "hi")))
  "hi"
  nil