When writing CGI programs, there are many problems which may affect their execution. Since these will not always be easily understood by examining the web browser output, there are other ways to check how your program is running:
First, check that your program runs by running it from the command line. It may be that you've made a syntax error, or that your program has the wrong permissions
Second, try opening it in a browser. If your program runs on the command line but does not output content to the browser, you may have forgotten to print out the Content-type: text/html header, or forgotten to leave a blank line between the header and the body, or may have made an error in your HTML output.
Thirdly, check the web server's log files. Where these are will vary from system to system. On our system, they're in /var/log/apache, and you can check them using cat, less, tail, or any other tool of your choice. If you don't know what these commands do, check their manual pages by typing man cat, man less, etc.
Look at the output of the hello.cgi script by pointing a web browser (such as Netscape) at http://hostname/~trainXX/cgi-bin/hello.cgi (replace hostname with the hostname or IP address of the training server, and XX with your number)
Modify hello.cgi to set a variable $name and include that name in the greeting. (Don't forget to use strict;)
Run your modified hello.cgi from the command line to ensure that it runs.
Press the Reload button in your browser to see if your modifications worked correctly.