You use async just to get a copy of the hash?

No. I used the async to demonstrate Storable work fine within threads; that the problem you encountered is with threads::shared::tie.

So yes, the threading was unnecessary to demonstrate that Storable works, but we know that already ;)

Also, how is that the copy created is not shared also?

Because nothing is shared unless you explicitly share it.

The reference to the shared hash %hash, simply results in a list of values. Placing them inside an anonymous hash constructor, constructs a thread-local (ie.non-shared), anonymous hash. Which Storable can nstore() in the usual way.

It is effectively the same as just: nstore { 1, 'a', 2, 'b }, 'fred.bin';. Except that the values come from a shared hash rather than constants.