One way to test whether your BASIC program and A-Shell are performing properly is to create a file that contains the expected stdin string, then just open a Command Prompt window and execute a command line which launches A-Shell with the redirected stdin file, and redirects output to another file. You can then examine the output file to see if it looks like a valid web page.
For testing purposes, stdin format input format can be simplified to a list of "VARNAME=value&" pairs, e.g.:
NAME=Bertrand Russsel&GAME=philosophy&
(The above example simulates a form with two variables, NAME and GAME.) Assuming this meets the requirements of your CGI program, and you stored it in a file called cgitst.in, you could test it with something like the following:
c:\vm\miame\bin\ashw32.exe -z -cgi -i c:\vm\miame\miame.ini cgicmd < ./cgitst.in > ./cgitst.out
Naturally you would adjust the paths, cmdfile name, and names of the input and output files as per your situation. If the process works, you should see no action whatsoever, but when you TYPE the cgitst.out file you should see a valid web page. Better yet, try to load it with a browser to verify that it is in a valid format. If this test works, then the only remaining issues would relate to the configuration of the web server.