If you think you have found a bug in perl, always test it against the most recent version - it may have already been fixed (as in this case). 5.10.0 may look new and shiny to a lot of people, but it's just 2 months shy of being 3 years old. And 5.10.1, 5.12.0, 5.12.1, and 5.12.2 have been released since.