Since I learned much of the basics of CGI programming from your course, which eventually lead me to the docs and several books, I was excited to see a new lesson. Very nicely done, I have only two problems with it (aside from those already meantioned): a reminder that one can use the OO form of CGI.pm might help some and a remind that not only can one type "perldoc CGI" but "perldoc -f <function here>" (for example, "perldoc -f exists" or "perldoc -f return"). On the whole though, great job and very helpful course.
"Cogito cogito ergo cogito sum - I think that I think, therefore I think that I am." Ambrose Bierce