Bitflip error

On Friday a colleague @work asked me about an error in a webapplication. There was a Perl syntax error in Sys::Hostname. As I saw no reason that anybody should mess with with Sys::Hostname, I checked the time Hostname.pm was last changed. Confusingly the last change was in 2004, apparently this was the time the server was set up. A diff with another Perl 5.8.0 installation showed a single bit change. The first space, 0x20, of Hostname.pm line 104 has turned into into a ‘(‘, 0x28. The only explanation I can imagine is that a bit has flipped in file cache.