These look like constant subs being redefined. I think that problem was fixed in later versions of Perl. It shouldn't cause a problem.
UPDATE: I just looked at the code and I see the problem. Business::OnlinePayment defines some subs using a routine called "build_subs", but doesn't check to see if they have been defined first. It shouldn't do that. Looks like it expected to run in a CGI environment and not be instantiated twice. This won't cause problems, but it will cause warnings. It would be easy to fix, by making minor changes to the new() sub in Business::OnlinePayment.