#include can't use a variable?

I haven't used #include previously, but is it not able to use a variable that holds the file path string?

Fails:

var doc = "/Desktop/TEST.jsxinc";

#include doc

Works:

#include "/Desktop/TEST.jsxinc"

I only ask because the folder path is dynamic and will vary, so I need to concat the folder path to the set file name.