$key = "\x4f\xcb";

for (1..10) {
    $key = pack('n',unpack('n',$key)+1);  # ++
    print unpack("H*", $key), "\n";
}

__END__
4fcc
4fcd
4fce
4fcf
4fd0
4fd1
4fd2
4fd3
4fd4
4fd5