The following assumes that the packet is in a stream of 1's and 0's.

    my $flag1 = substr $packet, 0, 8;
    my $byte_count = substr $packet, 9, 16;
    my $num_bytes = convert_byte_count($byte_count);
    my $payload = substr $packet, 25, $num_bytes * 8;
    my $flag2 = substr $packet, 25 + $num_bytes * 8, 8;
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The definition of convert_byte_count() is left as an exercise for the reader.

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