Quote:

Included scripts are not searched in the paths. They should be located in the work folder. Alternatively, their paths can be explicitely given in the #include statements or in PRAGMA_PATH statements.



-The Mighty Manual

PRAGMA_PATH is more convenient, but is only avaiable in >7.07

You can also use add_folder().

Also note that in Lite-C it has to be PATH and not path, I think.

shader tutorial