Functions can have multiple parameters:
ASSIGN/ADDANDDOUBLE=FUNCTION((A,B),2*(A+B))
Creates a function and assigns it to the function ADDANDDOUBLE. The function
takes two parameters, adds them together and then multiplies the result
by 2.
ASSIGN/V2=ADDANDDOUBLE(4,5)
Assigns V2 the value 18. The parameters 4 and 5 are substituted into the
expression portion of the function, thus becoming 2*(4+5).