So, CGI modules are usually an Exe. you pass it some input, either via the command line, or via some sort of text file, and it outputs HTML - either to the "standard out" or to a text file.
Obviously calling a program from clarion is real easy. Depending on how the program takes input, and delivers output, it's either trivial to interact with it, or mildly difficult.
We are using the PHP engine in exactly this way to support PHP pages. However we needed to create OddJob in order to pipe the input into the module (because it uses Standard In) and in order to capture the output (it outputs to Standard Out.) OddJob uses StringTheory, but between them it's pretty much no problem to run the CGI module.
cheers
Bruce