I'm not going to try to figure out what prunecheck is doing, it's certainly doing more than you describe (it's recursive, on doing different things based on the argument types).

But looking at the problem you describe, don't you want something like:

    %hash3 = %hash1;
    @hash3 {grep {exists $hash2 {$_}} keys %hash1} =
    @hash2 {grep {exists $hash2 {$_}} keys %hash2};
[download]

If not, then I don't understand what you want.

Abigail