Upgrading to Ubuntu 11.04 and on a new computer I noticed possible change behavior regarding directory listning from Perl:
my @files = readdir(DIR);
Earlier position zero and one of the array would contain . and .. while after the update I noticed . and .. could be found at other positions.
I did not search for the reason nor in Perl (modules for Perl would have changed during the update as well nor Ubuntu instead replaced readdir with handling of it.
If a general change / bug it would seem rather much code a bit all over would start behaving "odd".