Several kinds of messages can be set on an exit object (see "help messages" for instructions on doing so); they are printed to various audiences at certain times whenever an attempt is made to go through the exit. The ones whose names begin with 'o' are always shown prefixed with the name of the player making the attempt and a single space character. The standard pronoun substitutions (with respect to the player) are made on each message before it is printed; see 'help pronouns' for details.
The default message is given in brackets after each name below:
@leave [Verb not found]
Printed to the player just before they successfully use the exit.
@oleave [Verb not found]
Printed to others in the source room when a player successfully uses the exit.
@arrive [Verb not found]
Printed to the player just after they successfully use the exit.
@oarrive [Verb not found]
Printed to others in the destination room when a player successfully uses the exit.
@nogo [Verb not found]
Printed to the player when they fail in using the exit.
@onogo [Verb not found]
Printed to others when a player fails in using the exit.