Is it possible for a C program do decode this without requiring a browser.
However, beyond that, I really have no idea what you're asking. I gather you have a CGI on a web server, and you seem to be asking how to process its output on the client side. For this question the CGI may as well be written in GW-BASIC; its language is irrelevant.
What, specifically, do you need your C program to do? Do you need it to actually open a socket and communicate with the server, or only to parse the response text received some other way (how)? Unless there's more to this question, this has nothing at all to do with Perl.