Capturing return value of a function

Hi,

I have a function like this

CREATE OR REPLACE FUNCTION sp_insert(text, text, text, text)
RETURNS text AS
$BODY$
BEGIN
INSERT INTO tbl(a,b,c,d)
VALUES ($1,$2, $3, $4);

RETURN 'success';
END;

$BODY$
LANGUAGE 'plpgsql' VOLATILE;

I was wondering what would the function return if insert fails.
I want it to return 'success' upon a successful insert and 'failure' if
insert fails.

Would the following implementation work for that?

CREATE OR REPLACE FUNCTION sp_insert(text, text, text, text)
RETURNS text AS
$BODY$
BEGIN
BEGIN
INSERT INTO tbl(a,b,c,d)
VALUES ($1,$2, $3, $4);

RETURN 'success';
END;

RETURN 'failure';
END;

$BODY$
LANGUAGE 'plpgsql' VOLATILE;