Local Variables

So, the following trivial solution would give me local variables with a few simple combinators.

[ X -> Y = var X; _ = set Y (get Y + get Y); Y ] 7

If var stores a tree, then the result is a tree. If get retrieves a previously stored tree, then the result is a tree. If set stores a tree, then the result is a tree. If I am wrong, then f*ck it, and I am gonna call it an unsafe feature.