static S aToAn(S s) {
  ret jreplaceIC(s, "a", "an", new O {
    bool get(L<S> tok, int i) {
      S w = _get(tok, i+3);
      if (w == null) false;
      w = toLower(unquote(w));
      if (empty(w)) false;
      if (startsWith(w, "x ")) true; // what?
      ret contains("aeiou", w.charAt(0)); // rough
    }
  });
}