GOSUB ( expression )
CALL ( expression )
GOSUB is supported for backward compatibility, now FUNCTIONs and SUBs would be the preferred method.
Execution jumps to a subroutine marked by line label. Always use RETURN to exit a GOSUB, execution will continue on
next statement after GOSUB.
label may be defined as label: or as a SUB or FUNCTION
CALL for a FUNCTION or SUB is optional. When CALLing a FUNCTION the return value is discarded.
The version using an expression (parenthisis required) will compute the expression and then call the resulting address.