@include_file(filename)When you do this, you should be aware that it is treated like a subroutine call: a stack frame is created, and any symbols bound in script sections are local to the file. In addition, various parameters are localized. Therefore, you cannot define a new command or variable in an include file and expect it to persist past the end of the file.
5.10.1. Including code
5.10.2. Displaying Code