problem with plpgsql trigger function: parse error near ""

I just tried the trigger function from:
http://developer.postgresql.org/docs/postgres/plpgsql-trigger.html
(You can read the sql command on the bottom of this message.)

When inserting into emp table i got error: --> parse error near ""

I just wondering if any of you have the same probelem;
The plpgsql language was just created with createlang plqpsql [dbname]

Thank you
Yudie

Sample Code:
CREATE TABLE emp (       empname text,       salary integer,       last_date timestamp,       last_user text   );
   CREATE FUNCTION emp_stamp () RETURNS OPAQUE AS '       BEGIN           -- Check that empname and salary are given
      IF NEW.empname ISNULL THEN               RAISE EXCEPTION ''empname cannot be NULL value'';           END IF;
    IF NEW.salary ISNULL THEN               RAISE EXCEPTION ''% cannot have NULL salary'', NEW.empname;           END
IF;
           -- Who works for us when she must pay for?           IF NEW.salary < 0 THEN               RAISE EXCEPTION
''%cannot have a negative salary'',
 
NEW.empname;           END IF;
           -- Remember who changed the payroll when           NEW.last_date := ''now'';           NEW.last_user :=
current_user;          RETURN NEW;       END;   ' LANGUAGE 'plpgsql';
 
   CREATE TRIGGER emp_stamp BEFORE INSERT OR UPDATE ON emp       FOR EACH ROW EXECUTE PROCEDURE emp_stamp();