From the NannyMUD documentation

LAST CHANGE

2001-08-12

FUNCTION

NAME
        changed_exp_hook - 


AVAILABILITY
	/obj/player

DESCRIPTION
	This function is called when ever the experience points (XP)
	of the player is changed.

	ARGUMENTS

	changed_exp_hook(
	  ({ Experience,
	     Old experience,
	     The change
	  }),
	  the player
	)