That line appears in the docs for Business::PayPal::API, which isn't one of the modules I'm using. Thanks though for the heads up, I'll consider that one in the future.

I am having some luck with changing the $GTW variable in the IPN.pm file for the ::IPN module to the sandbox address, and then changing the entries for the live site with the sandbox address under the -address and -action parameters in the PayPal.pm of the ::PayPal module.

For any of you looking to do the same here is what I did:

#Line 21 of PayPal.pm (Business::PayPal)
address => 'https://www.paypal.com/cgi-bin/webscr' #change to https://
+www.sandbox.paypal.com/cgi-bin/webscr

#Line 82 of PayPal.pm (Business::PayPal)
        -action => 'https://www.paypal.com/cgi-bin/webscr', #do same a
+s above comment

#Line 13 of IPN.pm (Business::PayPal::IPN)
$GTW        = 'https://www.paypal.com/cgi-bin/webscr'; # do same as ab
+ove comments
[download]

When I go live I'll change these back to the live address.