how to correctly cast json value to text?

Hi

I am testing a new subscripting interface for jsonb, and I found one issue.

DO $$
DECLARE v jsonb;
BEGIN
  v['a'] = '"Ahoj"';
  RAISE NOTICE '%', v['a'];
END;
$$;
NOTICE:  "Ahoj"
DO

When I use this interface for reading, the jsonb type is returned. What is
the correct way for casting from jsonb text to text value? I would not
double quotes inside the result. Cast to text doesn't help. For operator
API we can use "->>" symbol. But we have nothing similar for subscript API.

Regards

Pavel