How do I make a form field required for a Perl Chat Script?

[SolitudeDude]

Hi all, New member here & also very new to Perl. I am running a CGI/Perl chat script on my website and have a problem. One of my rules is that all members register a valid email address during the registration process, however some users are able to get around this because there is nothing there to make the field "mandatory", they can simply leave it blank and still get into the chat. This chat comes with it's own registration & login forms that send the data to the CGI part of the chat and I would really like to know how to make at least the email field "required" with an error message if they leave it blank....any ideas? If needed, feel free to examine the chat yourself at www.decenttalk.org, or the script's homepage which is www.ralfchat.com It may take a little time to understand this program as it took me a while....it's a very sophisticated script but has excellent features. Thanks in advance for your time! Allen