unable to get perl pack to work in this case

Question

I ran following code

$a=pack("H1H3", "1","abc");
$b=unpack("B*", $a);
print "Got $b \n";

C:\Users\a0875499\Documents>perl abc.pl
Got 000100001010101111000000

Output looks incorrect to me. There is an extra "0000" which shouldn't be present. I am looking for output to be "0001101010111100". Do you know what I am missing?

Answer 1

The 'H' format for pack() assembles bytes, so if you supply an odd number of values it will pad out the last byte with a null nybble.

If I correctly understand what you want to achieve, you could do it with:

$a = pack("H4", "1abc");

or

$a = pack("H*", "1abc");