Making it work with lists is extremely difficult. I've thought many times about how I might try to make it work, but there's just no good way I can come up with. The problem is, list vars that are set to a value at compile-time are initialized via a hidden init proc; the actual value they use isn't stored anywhere.

The transform value for atoms and images is a different animal, however. It's stored internally in a way that makes it accessible, so it's actually designed for this purpose.