updated at a single element in a array using pl/pgsql

Can I update a single element in a array?

CREATE OR REPLACE FUNCTION TESTEARRAY() RETURNS CHAR AS '
DECLARE
v_array integer[];
BEGIN
v_array[1] := 10; -- Parser error at or near ''[''
RETURN v_array[1];
END;
'language 'plpgsql';

Cristian