getting number of rows updated within a procedure

I'm writing a procedure and I want to check the number of rows updated.
  But I can't figure out how.  I know UPDATE returns "UPDATE #" but I
don't know how to use that to get what I need.

Here's an example:

CREATE FUNCTION "test" () RETURNS int AS ' DECLARE
v_number_of_rows int;

BEGIN           update bigtable           set email_confirmed = 1
where user_group  = 1234;

-- and here, I want to know the number of rows updated
v_number_of_rows := *what?*;

END; ' LANGUAGE 'plpgsql';


Thanks.

--
Dan Langille
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