I looked at the code which required the "patch".

$ perl -MBusiness::OnlinePayment -we 'for( 1..2 ) { \
   my $tx= Business::OnlinePayment->new('AuthorizeNet'); 
}'
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From what I can tell, this is not a bug, because you are trying to redefine $tx as you work thru the loop.

Usually when you use multiple instance of a module, you name your "instances of the module" differently, like $tx and $tx1. Usually you would use a hash, like

my %tx;
for(1..2){ 
$tx{$_}{'object'}=Business::OnlinePayment->new('AuthorizeNet'); }
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The other technique is to only have 1 B::OP object going at any one time, and undef it at the end of each processing loop.

But I havn't actually tried the module, so I may be missing something. ;-)