ahAA! We've got a Heisenbug! I was thinking about this discussion after you mentioned you were running v5.18.1 and I was running v5.16.3. The failing tests depend on the order of elements in an array filled by keys. I installed perlbrew and perl-5.18.1 and failed a different set of tests.

The interesting thing is that with a perlbrew installed perl-5.16.3 (to prove that the failed tests were truly caused by the hash randomization feature introduced in v5.18), it still fails 2 tests and yet passes all tests on my fedora 19 packaged Perl 5.16.3 - wonders never cease.

In spite of it waking me up in the middle of the night, I feel quite pleased tracking that down. Think I'll treat myself to a lemon tart in the coffee shop while I re-think the test :)