Interface to HTTP gateway for PayPal's Payflow Pro service, as described on
the PayPal developer site at https://www.x.com/docs/DOC-1642

See also the developer area:
https://www.x.com/community/ppx/xspaces/web_checkout/payflow?view=documents

This module is intended to be a drop-in replacement for PFProAPI (a couple of
minor changes to your code are necessary to use this module instead of
PFProAPI).  The major difference is that it is pure Perl, and not architecture
dependent (ie, you can use this on your 64-bit FreeBSD platform.)