code: protected function isRaw($str)/*# : bool */
      {
          if (is_string($str)) {
              return (bool) preg_match('/[^0-9a-zA-Z\$_.]/', $str);
          } elseif (is_object($str) && $str instanceof RawInterface) {
              return true;
          }
          return false;
      }
docs: If $string contains any char other than '[0-9a-zA-Z$_.]', we consider
  it is a raw string case
  
  @param  string|object $str
  @return bool
  @access protected