Thanks for the great tip about debugging SSL.

You're correct, this is not a Perl problem.

Same delays when running the s_client test directly from OpenSSL.

The same test connects just fine to the Authorize.net gateway, so I'm taking this up with the Payflow development support folks now.

I'll report back just in case someone else has this problem, but as of now, it looks like it's related to certificate validation, or to Payflow's servers, or something

It's a shame the secular community isn't this helpful ;)