As I previously reviewed, functions in AHK rock! The below video demonstrates how easy it is to use the utilize the include command in AutoHotkey to leverage functions & libraries that are not in your main file. Without using the include command AHK will first look in your local library, then look under the myDocuments\AutoHotkey\Lib\ folder and finally under path-to-running-AutoHotkey.exe\lib\.
By using the include command you can specifically tell AHK to look in a given file.