Let me put it more clearly. If you looked at the modules suggested by other monks you would find out that the task is fairly easy even if you have to login. You can either use WWW::Mechanize to navigate to the login page, fill in the form, submit it and then navigate to that "particular link" and save content. Or you can use LWP::UserAgent to send the login information to the same URL the login form would send it making sure the cookies sent with the response are remembered by the LWP::UserAgent object and then download that particular link.

But I admit it would require that you look at the documentation of those modules and try to do something yourself.

Show us you tried and come back if you have problems, but don't expect to get a full script doing exactly what you ask for. This is not a free script service.