This is a common problem with iBeacons (and wives of geeks like us), and the simple solution is a software filter. You must ignore region exit events that last only a few seconds until you verify that there is no subsequent entry event.
You can do this by creating a variable (e.g justExitedRegion) that tracks these events. When you get an exit region notification, set justExitedRegion=YES and start a five second timer. When the timer goes off, if justExitedRegion==YES, perform your exit logic normally and set justExitedRegion=NO. Otherwise skip processing the exit logic.
Meanwhile, if you get an entry notification and justExitedRegion==YES, set justExitedRegion to NO and skip your entry processing.