Consider this example:
This is MyInclude.au3
#Include-once
Func Abc()
Msgbox(0,'','Hello from "ABC" ')
EndFunc
Func Def()
Msgbox(0,'','Hello from "DEF" ')
EndFunc
This is my main script:
#include <C:\Folder\MyInclude.au3>
Abc() ;Runs OK if Def() is commented out
Def() ;Produces...