# v1 is a little-endian 16 bit (short) so needs 2 bytes
# if substr didn't limit to 2 bytes substr($raw,1) works also
# unpack will use first 2 bytes.
my ($len) = unpack 'v1',substr($raw,1,2);#substr deals in bytes not nibbles.
print $len,"\n";                          #prints 71
print unpack ('v', substr($raw,1)),"\n";  #prints 71
print unpack ('x v', $raw ),"\n";         #prints 71