Do you mean "Print all the variables I've defined in my subroutine" or "Print all the variables I'm returning from my subroutine" or some other group of variables?

You either need to know the name of some thing or the index to the thing ( in very general meaning of name and index ) in order to manipulate a thing. If you know the name of it just print the name. If you know the index of it then dereference to get the name. If you don't know the name ahead of time and you don't have an index to it; then you can't reference it. Simple.