Yesterday esteve and I tried to see whether Acme::Pythonic could run on 5.6.1, currently it requires 5.8.0. We found what seems a bug in a regex, and looked like the only detail to change is the use of constant HASHREF in some tests.
There was a mysterious combination in that machine that made Test::Harness report successful tests as failures. We tried to reproduce it in a couple of machines with the same versions of Test::Harness and Test::More (the last ones) but we couldn't.