Example 8-3 Forward Declaration for a Nested Subprogram

DECLARE
   PROCEDURE proc1(number1 NUMBER);  -- forward declaration
   PROCEDURE proc2(number2 NUMBER) IS
      BEGIN
        proc1(number2);  -- calls proc1
      END; 
   PROCEDURE proc1(number1 NUMBER) IS 
     BEGIN
      proc2 (number1);  -- calls proc2
     END;
BEGIN
  NULL;
END;
/