Doing that is not enough. The POST request must be converted into a GET request by the agent and its content removed. That's Netscape's exact behavior, as far as I remember (I wrote this code about a year ago). This snippet in my code does it:

    if($request->method eq 'POST') {
        $referral->method('GET');
        $referral->content('');
    }
[download]

Last time I checked UserAgent was not doing this as a result of overriding redirect_ok().

Update: This is a reply to Merlyn's original post, in which redirect_ok simply returned a 1.