I am trying to see if I can use something like the following code sample from the Oracle PL/SQL documentation, but I can't figure out the syntax for how to execute this procedure...what would the first parameter look like when calling it? Here it is:

CREATE PACKAGE emp_data AS
TYPE GenericCurTyp IS REF CURSOR;
TYPE EmpCurTyp IS REF CURSOR RETURN emp%ROWTYPE;
PROCEDURE open_emp_cv (emp_cv IN OUT EmpCurTyp, choice NUMBER);
END emp_data;

CREATE PACKAGE BODY emp_data AS
PROCEDURE open_emp_cv
(emp_cv IN OUT EmpCurTyp,
choice NUMBER) IS
BEGIN
IF choice = 1 THEN
OPEN emp_cv FOR SELECT * FROM emp WHERE comm IS NOT NULL;
ELSIF choice = 2 THEN
OPEN emp_cv FOR SELECT * FROM emp WHERE sal > 2500;
ELSIF choice = 3 THEN
OPEN emp_cv FOR SELECT * FROM emp WHERE deptno = 20;
END IF;
END open_emp_cv;
END emp_data;

Could you call this directly from SQL*PLus, like:
exec emp_data.open_emp_cv(????,2); ??

Or would you have to have already selected a row (or multiple rows) from emp and call it from there???

Thanks in advance