I'm wondering if the problem is the path to your local file: "/home/testuser/filestore/WWWMSEXP.TXT"
That looks like a unix path, Unless you have your windows computer set up with that kind of directory path, you will have issues. You will probably get a better picture of the exact error if you add the $! symbol to your die message, like so:
$ftp->get($getname,$file_name) or die "can't get file: $!";