static class FRegExp extends FunctionImpl {
  static boolean debug;
  String re;
  
  *(String *re) {}
  
  public O process(Object _in) {
    String in = cast _in;
    Matcher matcher = Pattern.compile(re).matcher(in);
    boolean found = matcher.find();
    if (debug)
      debug("found: " + found + ", regexp: " + re);
    if (found)
      return matcher.group(1);
    else
      return "";
  }
  
  public void toJava_process(Code code) {
    code.line("Matcher m = Pattern.compile(" + javaQuote(re) + ").matcher(" + code.s() + ");");
    code.assign("m.find() ? m.group(1) : \"\"");
  }
}

Began life as a copy of #1000584