But what is the best practical solution for this task?

But what is the task? Is it to access the "next" key/value element of the hash in the inner loop? If so, then an array structure would seem more appropriate since a hash has no inherent order beyond key-value pairing (but there are tie-ed, ordered hashes). (Update: As to copying, if you make a copy of the hash by value, you will just end up with two independent each iterators for each copy. If you make a copy of the reference, you're still just operating on the same hash referent!)

What output do you want from your code?