static Map<S, java.util.regex.Pattern> compileRegexp_cache = syncMRUCache(10);

static java.util.regex.Pattern compileRegexp(S pat) {
  java.util.regex.Pattern p = compileRegexp_cache.get(pat);
  if (p == null) {
    ifdef compileRegexp_debug
      print("Compiling regexp: " + pat);
    endifdef
    compileRegexp_cache.put(pat, p = java.util.regex.Pattern.compile(pat));
  }
  ret p;
}

Began life as a copy of #1012521