if ($received_data) {
   my $here = 0;
   my $next_value = sub { 
      my $width = shift; 
      my $start = $here;
      $here += $width;
      return oct("0b".substr($received_data, $start, $width));
   };
   my $server_li = $next_value->(2);
   my $server_vn = $next_value->(3);
   my $server_mode = $next_value->(3);
   my $server_stratum = $next_value->(8);
   ...