Optimizing Pl/PGSQL stored proc (nested conditionals)...

Howdy. I've got a quick snippet below of a stored procedure that sets
utc_end_date to the time when the row is disabled. The reverse is
true also that if it's enabled, then it will remove the utc_end_date
and set it to NULL. Anyway, I had to use nested IF blocks because I
couldn't get the case or switch statement to work. Is this the most
optimal way to do this? -sc

/* Validates and sets the end_date */
CREATE FUNCTION update_enabled() RETURNS opaque AS '
BEGIN
IF NEW.enabled = ''y'' OR NEW.enabled = ''n'' THEN
IF NEW.enabled = ''y'' THEN
NEW.utc_end_date := NULL;
ELSE
NEW.utc_end_date := (SELECT NOW());
END IF;
ELSE
IF NEW.enabled IS NOT NULL THEN
RAISE EXCEPTION ''Invalid enabled value (%): can be only (y) or (n)'', NEW.enabled;
END IF;
END IF;
RETURN NEW;
END;
' LANGUAGE 'plpgsql'

--
Sean Chittenden