--PROCEDURE

CREATE OR REPLACE PROCEDURE my_procedure(

   p_in_param1 IN NUMBER,

   p_out_param OUT VARCHAR2)

IS

BEGIN

   -- Procedure body goes here

   p_out_param := 'Hello, world!';

END; 

DECLARE

   my_var VARCHAR2(100);

BEGIN

   my_procedure(123, my_var);

   DBMS_OUTPUT.PUT_LINE(my_var);

END;