static boolean putMatch(Map<S, Lisp> matches, S key, Lisp val) {
  if (matches.containsKey(key))
    fail("multi-matching not implemented");
  matches.put(key, val);
  ret true;
}

static boolean putMatch(Map<S, Lisp> matches, S key, S val) {
  ret putMatch(matches, key, lisp(quote(val)));
  }