sub Hex2Bin {
        $hex = $_[0];

        %h2b = ( 0 => "0000", 1 => "0001", 2 => "0010", 3 => "0011",
                4 => "0100", 5 => "0101", 6 => "0110", 7 => "0111",    
                8 => "1000", 9 => "1001", a => "1010", b => "1011",
                c => "1100", d => "1101", e => "1110", f => "1111");

        (my $binary = $hex) =~ s/(.)/$h2b{lc $1}/g;

        return $binary;
}