DEBUGGING

You can see the raw SOAP XML sent and received by Business::PayPal::API by setting its $Debug variable:

$Business::PayPal::API::Debug = 1;
$pp->SetExpressCheckout( %args );

this will print the XML being sent, and dump a Perl data structure of the SOM received on STDERR (so check your error_log if running inside a web server).

If anyone knows how to turn a SOAP::SOM object into XML without setting outputxml(), let me know.