You'll need to take a look at your apache error log to see what the "internal server error" is. The four most likely cases (in my experience) would be:
- The CGI program is in a directory which does not have CGI execution enabled.
Solution: Add the ExecCGI option to that directory via either httpd.conf or a .htaccess file.
- Apache is only configured to run CGIs from a dedicated cgi-bin directory.
Solution: Move the CGI program there or add an AddHandler cgi-script .cgi statement to httpd.conf.
- The CGI program is not set as executable.
Solution (assuming a *nix-type operating system): chmod +x my_prog.cgi
- The CGI program is exiting without sending headers.
Solution: Run the program from the command line and verify that a) it actually runs rather than dying with a compile-time error and b) it generates the correct output, which should include, at the very minimum, a Content-Type header and a blank line following the last of its headers.
