Are you saying that the error has nothing to do with whether or not that form field whose value is requested exists in the form? Because that is what the error message leads me to believe.
I have initiated the CGI as seemed to be indicated in the package description, even copying the example verbatim. But try as I might, it doesn't work.
It seems that it is quite new. There are no examples of code using CGI::Tiny that I was able to find online beyond that which I've already tried that comes with the package itself. Sigh, it looks like I'll just have to go back to good ole CGI.