sub mk { join '', sort @_ }

$hash{ mk 'a', 'b' } = 'Some Value';
print $hash{ mk qw{ b a } };

##</code><code>##

if ( $tests{ $refA } && $tests{ $refB } ) {
 # This checks two hash entries very cleanly, but falls down
 # if the results are dependent on whether A and B are tested together.
 
# some stuff

}