The "Express Interface Specification" linked from that page is the document which I previously referred to as "rather less than useful". As in "it only provides a single sample of credit card processing (on page 134), which just instantiates a bunch of classes from an unspecified C# library and then has them do all the work". Or perhaps the ElementExpress.* classes are built in to the C# core, so there isn't a library to identify. I'm not familiar enough with C# to say. But they're definitely not in the Perl core, so an example of using them does me no good whatsoever.

Now, yes, I expect that I probably can work something up which directly generates a lump of XML to submit based on their lists of "input fields" and extracts the response from the returned XML based on the corresponding lists of "output fields", but that's precisely the wheel I'd like to avoid reinventing. Take a look at the Business::PayPal modules for an idea of what I'd hoped to find - a set of Perl classes which I can instantiate and then have them do all the work.