my $ua = LWP::UserAgent->new;
my $uri = shift @ARGV;
my $headreq = HTTP::Request->new(HEAD => $uri);        
my $headres = $ua->request($headreq);        
my $statuscode = $headres->code();        
if ($statuscode == 401) {
   my $final_uri = $headres->request()->uri();   # <----
   print "Status 401 at $final_uri\n" 
}