A typical CGI script outputs some HTTP header lines, a blank line and then your HTML document. You can usually run the simple scripts, redirecting the output to a temporary file. Edit the temporary file to remove the HTTP header lines, save the remainder and then view it in a web browser. It's inconvenient but barely usable in restricted environments.

If you are forced to keep working that way you'll devise some scripting automation (sed, awk or perl) to trim off the HTTP header lines. With a bit more effort you could create your own web server in Perl with modules such as HTTP::Server::Simple to send the CGI output directly to the browser. Even better would be to swap CGI for PSGI as used for example Dancer, but that might be forbidden on your AIX computer.