When you stringify a reference, it no longer is a reference -- it's just a plain old string that happens to contain a human-readable representation of an address and a data type. So the code above is doing just what it would do if your initial hash assignment read:
%hash = ("ARRAY(0x80fbb0c)" => "STUFF");
If you turned on
strict, you'd be warned that a string can't be used as an array reference.
Hash keys must be strings, not references. If you want to "dereference" something, you probably should be storing the reference itself as a hash value, so you can use it directly and not need to dereference it in the first place.
$perlmonks{seattlejohn} = 'John Clyman';