my $packet_template = "B16 s2 A4 A8 A2 A A A3 C2";

# read in next record from STDIN and store in $buffer

($Flags,$x,$y,$Mode3,$Callsign,
    $Route,$Spare1,$Spare2,$Flight_Level,
    $Terminator,$Checksum) =
  unpack ( $packet_template, $buffer );