Using the sha-bang as you did in your script should be enough. Otherwise you can create a test user and assign /bin/tcsh as the default shell, so that you have a complete login environment to test with. Regarding the Undefined variable
error, it's really strange. Is the echo command inside the script?
Finally, a good reference for csh is www.kitebird.com/csh-tcsh-book/csh-intro.pdf
. Hope this helps.