Haskell memory management

Haskell can't update variables, so I came up with an alternative solution: make new variables that hold desired values. But the problem is that when I make a new variable every time I change its value, the old variable stays there and littler the memory. How can I delete it?

I am Heron of Alexandria. I have a large beard and I create mathematical formulas. If you don't repost this comment on 10 other pages, I will use my primitive steam engine to induce mold in your walls.