my $eight_bit_piece = 255;
my $other_eight_bit_piece = 255;
my $sixteen_bit_piece = 8;

my $packaged_data = pack("CCn",
    $eight_bit_piece,
    $other_eight_bit_piece,
    $sixteen_bit_piece);
# Gives me 11111111 11111111 0000000000001000 as desired