"It is impossible for you to refer to a Perl variable, such as $mydata, in the web-page text that you send to the client, because the client has no idea where the web-page came from and has no access at all to the (Perl) software that may have produced it."

Proving once again that you have no idea what you're talking about. This is possible and quite common. You replied after other users provided working example code (an alien concept to you I know) that shows how to achieve this.