3
By "CGI include", do you mean a Perl script? (Perl scripts typically use the extension .cgi, so often people refer to Perl as CGI, which isn't really accurate.)
The easiest method would be for the Perl script to store its results in a file, which a custom XOOPS block or module could read and display.
Automatically executing a Perl script via an HTTP request from a PHP script should be possible, but that gets tricky.