Attunement custom enchantment (HELP)

I'm looking for a way to make a custom "Attunement" enchantment. Basically, I want items with this enchantment to persist on death, like keep inventory for specific items. I know how to store the item data as a variable, but I also need to use two separate procedures for this enchantment. One to trigger on entity death, and one to trigger on player respawn. How do I get the variable data from one procedure to the other?