Section 14.12: Variable IDs Up Chapter 14: Extensions Section 14.14: Embedded C code.  

14.13 Passing IDs

Passing IDs to functions is one of the implications of Variable IDs. It will allow you to use _variable(str) to name objects passed to functions, even in another module.
 Section 14.12: Variable IDs Up Chapter 14: Extensions Section 14.14: Embedded C code.