parse error for function def

CREATE FUNCTION base.fn_fkey_check(text, text, int4) RETURNS bool AS
'DECLARE
BEGIN
RETURN (SELECT count($1) FROM $2 where $1 = $3)::bool;
END;'
LANGUAGE 'sql';

produces this error
ERROR: parser: parse error at or near "RETURN" at character 20

I'm trying to create a function to use on a trigger to check reference
to views since pg does not support foreign keys referencing views.

--
Terence Kearns ~ ph: +61 2 6201 5516
IT Database/Applications Developer
Enterprise Information Systems
Client Services Division
University of Canberra
www.canberra.edu.au