Integrating Google invisible recaptcha into formmail.pl

I use formmail.pl on all my websites for the Contact Us form. On one of them, the landing page for my domain sales, I am getting a lot of SPAM form submissions.

Has anyone integrated invisible recaptcha into formmail? Or what is the best submission form, free script software to use these days, and then integrate invisible recaptcha into?

Here is the contact us form I have up
xynames.com
I assume I must modify both the html for the submission form and the formmail script.

I would like to integrate the recaptcha into my existing SEND NOW button.

There is literature on the web about integrating regular recaptcha into formmail, but not invisible recaptcha.

The formmail I use is perl, anyone here good with perl? I am a decent website creator with HTML and java but I haven't done a lot of perl in a long time.

Is it formmail.cgi? I thought no site used that any more. What a blast from the past.

I'd rewrite it in PHP for a modern website. Easy to find recaptcha PHP code on the WWW.

I have both versions one is perl and one is PHP. I've experimented with both.

For some reason the perl formmail has less of a tendency to send legitimate messages that end up in my spam inbox, so I stuck with the perl version.

The version I use of formmail is Matt's perl formmail.

Someone else recommended I use the NMS version of formmail, also perl.