The problem is that, there is a variable is the iframe URL. For example, [remoteurl?random=12345....] This var (random) does not repeat in any 3 days. So, although it is not hard to get the source URL of the iframe, you cannot simply use LWP to get the contents of the destination page. (since the random ID you use in your LWP agent tried to visit a repeated random ID, which is not allowed).
Any suggestion? Thanks!