Another easy one but this is really useful when you need to string various rule files together. Just modify this to meet your needs:
import yourrulefile : "yourrulefile.cga" Lot--> 10% : yourrulefile //this calls the rule file specified above 90% : another // change this to whatever you want perhaps another rule file? else : NIL // change this to whatever you want perhaps another rule file? another--> color("#000000")