static <A, B> void mapPutVerbose(S mapName, Map<A, B> map, A key, B value) {
  if (map != null && key != null && value != null) {
    B old = map.put(key, value);
    if (!eq(value, old))
      print((old == null ? "Adding to" : "Updating") + " \*mapName*/: \*key*/ => \*value*/");
  }
}

Began life as a copy of #1007227