From dm4.pdf, the advanced manual on inform6:

  Object  -> "flashlight"
    with  name 'flashlight' 'torch',
          description "It's a battery-powered flashlight, of the sort that switches on and off.",
          after [;
            SwitchOn:  give self light;
            SwitchOff: give self ~light;
          ],
    has   switchable ~on ~light;