Syntax:  Alone shows your current message. 
          .set exitmsg <message>        lets you put a message in.
          .set exitmsg [clear|-c|none]  resets to default

Results:  When you walk out a room, instead of "<user> goes to the <room>"
          it shows "<user> <your exitmsg>" If you don't change your
          message from the default it will put the room name you are going
          to at the end.
          This message is saved to disk between logins.

See also: go, set_entermsg