You don't say what actually happens when you try to use Mail::DeliveryStatus::BounceParser after futzing with the file. How exactly does it not work? And why are you wrapping it in an eval block and ignoring any errors it throws? Try adding this after your call to new():

warn "Call to new failed: $@" if $@;

Then tell us what it says - quite likely it will contain a description of the problem!

-sam