Accidentally, I deleted a perl folder (/System/Library/Perl/5.8.8/darwin-thread-multi-2level) which caused perl to stop working. I feared I'd have to reinstall Leopard but with Pacifist I was able to look in the package files on my installation DVD. The reinstall took a mere 2 minutes.. SWEET! I only hope that the 10.5.1 update didn't touch any of the files I had to restore.