I can replicate that with ActivePerl 5.10.0 build 1004. The 5.10.0 behaviour is buggy. Hopefully, it's been fixed for 5.10.1. RC1 of 5.10.1 was just released, so it's probably too late to fix it for 5.10.1 if it's hasn't already been fixed. Does someone has 5.10.1-RC1 handy?