docs: function parse_balanced(re_open, re_close, re_rest) {
    result = match(re_rest);
    while (look(re_open)) {
      result += match(re_open);
      result += parse_balanced(re_open, re_close, re_rest);
      result += match(re_close);
      result += match(re_rest);
    }
    return result;
  }