I have managed to get the script working, though am aware there are several things to be done to improve it, primarily in optimising email address validation, and in getting the form field values - oko1's and Jenda's words of wisdom, and indeed everyone else's, have given me much to meditate upon. Phrases like 'reinventing the loop' spring to mind, but it's useful practice for me.

I'm loth to post acres of pre-competent code here, but if anyone needs a shudder, do feel free to have a look at the form code and/or the Perl code.

I'm overwhelmed by the response from this forum, muchas gracias senors, mucho gusto. What started as an optimistic 2-hour hack of someone-else's code a week ago seems to be turning into an obsession.