IRIS and Caché / Ensemble offer the possibility to add Languages Extension as SystemFunctions, SystemVariables, SystemCommands
The related documentation tells you where to add the system-wide extension. Parameter passing is not covered explicitly.
In principal, it is always a call for a subroutine. And at the end, you terminate with QUIT returning a value or not.
You call them as any other standard system function with all required parameters in parenthesis.
eg $ZZR(47,11) and it will be processed. Just mentioned for completeness.
There are 2 use cases: requesting a value WRITE $ZZR or setting a value SET $ZZR=17
The related common function has to detect what is going on. Like this:
This is a little bit tricky as a distinction between multiple arguments and multiple parameters is required.
Multiple arguments are separated by a comma "," : ZZR arg1,arg2,..
But if you require more than a single value as parameters
they have to be separated by colons ":" : ZZR par11:par12:par13, par21::par23, ::par33, par41, :par52
or just nothing ZZR
The code should be prepared to handle missing parameters.
It is the decision of your code if the last parameter is interpreted as a timeout or anything else.
It is typically ended with QUIT without returning any value.