Or a little more plainly (update to explain: using the names the OP did, so he can see what corresponds): 
sub hd {
  my ($k, $l) = @_;
  my $diff = $k ^ $l;
  my $num_mismatch = $diff =~ tr/\0//c;
}

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Caution: Contents may have been coded under pressure.

In reply to Re^2: Hamming Distance Between 2 Strings - Fast(est) Way? by Roy Johnson
in thread Hamming Distance Between 2 Strings - Fast(est) Way? by monkfan

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