in reply to Problem with LWP, frames, login, and parent.main.location.replace()
My guess is that there's some sort of state checker being used, such as a cookie or a hidden field, or if they're pretty dumb, the referer string.
You'll probably need to note if any cookies are being sent back from the login request, or if there's a hidden field in the response form. Cookies can be managed nearly painlessly with HTTP::Cookies. Forms can be extracted from the response with HTML::Form.
In Section
Seekers of Perl Wisdom