static Map<S, Pair<S, SS>> mechHashMap_cache = synchroMap();

static SS mechHashMap(S listName) {
  Pair<S, SS> p = mechHashMap_cache.get(listName);
  S text = mechList_raw(listName);
  if (p != null && eq(p.a, text)) ret p.b;
  S parsing = first(mechList_opt(listName + " | Parsing"));
  p = pair(text, (SS) (parsing != null
    ? asHashMap((SS) callAndMake(parsing, text))
    : parseDoubleArrowMap(new HashMap, tlft(text))));
  mechHashMap_cache.put(listName, p);
  ret p.b;
}

Began life as a copy of #1014197