SQL> create or replace procedure p_test (par_depts in varchar2)
  2  is
  3    cursor cur_emp is
  4      select deptno, ename, job
  5      from emp
  6      where deptno in (select regexp_substr(par_depts, '[^,]+', 1, level)
  7                       from dual
  8                       connect by regexp_substr(par_depts, '[^,]+', 1, level) is not null
  9                      )
 10      order by deptno, ename;
 11  begin
 12    for cur_r in cur_emp loop
 13      dbms_output.put_line(cur_r.deptno ||': '|| cur_r.ename ||', '|| cur_r.job);
 14    end loop;
 15  end;
 16  /

Procedure created.

SQL>

SQL> with test as (select '10,30,3' col from dual)
  2  select regexp_substr(col, '[^,]+', 1, level)
  3  from test
  4  connect by regexp_substr(col, '[^,]+', 1, level) is not null;

REGEXP_
-------
10
30
3

SQL>

SQL> declare
  2    l_depts varchar2(20) := '10,30';
  3  begin
  4    p_test (l_depts);
  5  end;
  6  /
10: CLARK, MANAGER
10: KING, PRESIDENT
10: MILLER, CLERK
30: ALLEN, SALESMAN
30: BLAKE, MANAGER
30: JAMES, CLERK
30: MARTIN, SALESMAN
30: TURNER, SALESMAN
30: WARD, SALESMAN

PL/SQL procedure successfully completed.

SQL>