Help with quotes in plpgsql

[Richard Ray <rray(at)mstc(dot)state(dot)ms(dot)us>]

How should this be properly quoted

create or replace function test(integer) returns setof text as $$
declare
  a record;
begin
  select into a now() - interval '$1 day';
  return next a;
  return;
end
$$ language 'plpgsql';

I'm not having a lot of luck
Thanks
Richard