Swapping Snacks
	(Switching items in an array)

The Story

	In Mrs. Schwane's Kindergarden class, everyone can eat the snack that they like best. There's chocolate chip cookies, brownies, cupcakes, spaghetti, confetti, and carrots. (Nobody ever eats the carrots...) However, sometimes these crazy little Kindergardeners change their minds. Right after Mrs. Schwane passed out the snacks to all her students, two little girls wanted to eat something different. 
	At first, it was simple enough to fix. Lucy was the only one with a problem:
LUCY wanted to have the snack that MARIA got.
	Maria had a brownie. So Mrs. Schwane took Lucy's snack, and went back to the cabinet to trade it for a brownie. She gave the brownie to Lucy, and for the moment it seemed like everything was going well, when suddenly Maria burst out into tears:
Maria wanted the snack that Lucy had originally.
	OH NO: Poor Mrs. Schwane couldn't remember what snack Lucy had before!
	To make matters worse, Maria was from Spain and didn't speak much english. She didn't know what the snack was called.
FORTUNATELY for Mrs. Schwane, she remembered she STORED Lucy's snack on the TOP SHELF. She raced back to the cabinet to give it to Maria, and at last everyone was happy.

Wait, what happened exactly?

LUCY wanted MARIA's snack.
Mrs. Schwane stored LUCY's snack on the top shelf, and then gave her a snack like MARIA's.
Then MARIA wanted LUCY's ORIGINAL snack.
Mrs. Schwane retrieved LUCY's ORIGINAL snack from the top shelf to give to MARIA.

How could this look in code?

$topshelf = @snacks[LUCY];
@snacks[MARIA] = @snacks[LUCY];
@snacks[MARIA] = &topshelf;