Subtly different. Originally I didn’t have ^a, but you do in-fact need it. ^a means “push with no evaluation” and (a) means “build a closure” that computes a”.

If you push, pop, push, pop, push repeatedly you’ll be wrapping the value in lots of closures. The value is no longer a value too. You’d have to “force” it to get back the value.

Semantically quite different. If you’re going all Turing tarpit, could you survive without “^a”? Maybe. But you’d be suffering for sure.