I built perl 5.8.8 today from source, on a machine where I've done this successfully several times before. Some of the tests failed, so I ran the failing tests by hand to see if I could figger out what the hell was going on. They passed. Running 'make test' again, they all passed.
GOD DAMN WERNER HEISENBERG!
When I mumbled about this on irc, pjcj pointed out that "perl is designed to make you doubt your sanity".
So GOD DAMN H.P.LOVECRAFT TOO!