code: public function returnsByReference($method, &$reference, $args = false)
      {
          $this->dieOnNoMethod($method, 'set return reference');
          $this->actions->register($method, $args, new SimpleByReference($reference));
      }
docs: Sets a return for a parameter list that will be passed by reference for all calls.
  
  @param string $method       Method name.
  @param mixed $reference     Result of the call will be this object.
  @param array $args          List of parameters to match including wildcards.