The syntax between your two examples is the same in that it uses the #define preprocessor directive. It seems you are confused by the last argument in the #define directive. In the examples you referenced, the last argument refers to pre-defined C-Macros in PLECS. The different macros allow you to access block data such as input/output signals, parameters, and states.
Refer to the C-Scripts + C-Script Macros section of the PLECS Manual for a description of the available macros. The graphic pasted below shows a subset of the available macros.