I haven't tried to run tclsh script myself, but I went to that page and pull the URL out the form and plugged it into the address bar. Mozilla asked to save score.tcl and it ends up I got the source code. Have you set the permissions correctly to 0755 ? Assuming it still doesn't work after setting the permissions, here are some snippets from the Apache manual:
The source code of your CGI program or a "POST Method Not Allowed" message
That means that you have not properly configured Apache to process your CGI program. Reread the section on configuring Apache and try to find what you missed.
The above directive tells Apache to permit the execution of CGI files. You will also need to tell the server what files are CGI files. The following AddHandler directive tells the server to treat all files with the cgi or pl extension as CGI programs:
AddHandler cgi-script cgi pl
Try adding this to an .htaccess file:
AddHandler cgi-script tcl
The GET method would work if the script is able to read the QUERY_STRING enivornment variable, however that script is written to only read the STDIN filehandle.