Returning an array form a function

Hi,

I'm trying to return an array from a postgres function, but I keep
getting weird errors:

-- this works
CREATE OR REPLACE FUNCTION test(float4[])
 RETURNS float4[]
AS '
BEGIN
 RETURN $1;
END;'
LANGUAGE 'plpgsql';

select test('{1,2}');

-- but I want to change the values in the array:
CREATE OR REPLACE FUNCTION test(float4[])
 RETURNS float4[]
AS '
DECLARE
 a_return[] float4;
 -- a_return[2] float4;
BEGIN
 a_return[1] := 1;
 select 2 into a_return[2];
 RETURN a_return;
END;'
LANGUAGE 'plpgsql';



I just can't seem to declare an array.  How should I be doing this?