Reverse brute force.
It is sort of brute force in the reverse, rather than checking each element as it comes, you are making an equivalent object and checking it. The means that you are generating it by are not brute force by abstraction, but in actual implementation they might be, which really depends on the algorithm employeed in the operators which you used (I've never read the PERL souce to those operators, so I don't know). Still, it is a very elegant piece of code, and I know that I enjoyed it :-)

"We're all different!"
"I'm not"
-The Life of Brian