sS ai_simplifyNP_2(S s) {
  loop: for (S pat, pat2 : mechMap("Noun simplification patterns")) {
    SS map = matchDollarVarsIC_plusBrackets(pat, s);
    if (map == null) continue;
    for (S var, val : map) {
      if (startsWith(var, "$noun") && !isNoun(val)) continue loop;
    }
    ret replaceVars(pat2, map);
  }
  ret s;
}