void on_depart( object who, string moveverb, string direction,
   object destination )

Called whenever a living object leaves the room; all other objects in the
room will receive this event. The moveverb is the type of motion (I don't
have a comprehensive list of such as present, but "walk", "stairs", and
"climb" might be possible values). The direction is the name of the exit
they're leaving through, and might be something like "second store". The
destination is the object to which they will move.

You can't affect the motion from this event. If you want to do that, you
need to look at setting up a blocker first.

FOR SCRIPTS: on_depart

Called when something leaves the room. Actors is the thing that leaves, 
and Target is where they're going. There are also two vars set: Get( "dir" 
) tells you the direction they left, and Get( "moveverb" ) tells you what 
verb they used to go.

