first i wouldn't use that script at all,
i think there's some issues with the game recognizing your skill level for certain things when you use setAV, setAV actually changes the base value of your player.
http://www.creationkit.com/index.php?title=Actor.SetAV_(Papyrus)
if anything you'd want to use ModAV, but making a permenant effect might be better through a perk than through a script.
I would just add whatever you wanted to the cannibal perk, if you can't add anything to it, then just add
akActor.ModAV("Health", 1.0)
to the OnEquipped Event
and
akActor.ModAV("Health", -1.0)
on the OnUnEquipped Event
both within the if endif blocks.
i would assume that if you don't set your health back down the same amount on UnEquip it will just keep piling on 1 health everytime you equip the ring.
http://www.creationkit.com/index.php?title=ModActorValue_-_Actor