keys(@array) has a defined meaning that is consistent with the array-as-unbroken-sequence model that is used in most places. To change it to implement the equivalent operation for the sparse-array model would be disruptive. We shouldn't do that. If you really like the discouraged sparse arrays and want a key-listing operation for them, you should implement that as an XS module and put it on CPAN. This ticket should be closed. -zeframThread Next