Not really a Perl issue, I'd guess your /usr partition is mounted as read-only. The following for Linux (there are differences if you're using a different *NIX): Check /etc/mtab, that will give you the currently mounted partitions with mount options, check whether your /usr is mounted rw or ro. If it's ro and you're sure that there isn't a very good reason why this is the case (I mean sure here btw, like in absolutely SURE), you can issue

That should fix your problem.