Try using Data::Dumper on the return from new().

print Dumper $mail; to see if the is anything useful in there.

I took a quick look at the source, and it would appear that new() returns a valid handle regardless of whether it managed to read anything or not. In fact, from my cursory glance, I couldn't see much in the way of error handling/reporting at all, but it maybe that this is buried further down in the hierachy of modules.

You'd think that you would get some indication of whether it failed to read the from file handle supplied. I couldn't see anything mentioned about what happens in the event of failure nor how to test for same?