Congratulations, you have found a bug!
I've added it as https://github.com/pjcj/Devel--Cover/issues/41 and then I fixed it as https://github.com/pjcj/Devel--Cover/commit/929b7fa
This will be in the next release, or if you can't wait that long grab it from github and use that.
If you still have problems, please reopen the ticket.
in reply to build testcover fails because of non taint-safe used module