If the strings/strands being compared are all the same length, bitwise-xoring the strings effectively compares them. The tr operator can then be used to flag and count positions of equality. IIRC, GrandFather had a note on this a few months back. 
>perl -wMstrict -le
"my ($x, $y) = qw{abXcdYef pqXrsYtu};
 my $diff = $x ^ $y;
 $diff =~ tr{\x00-\xff}{=!};
 print $diff;
 print 'number of differences: ', $diff =~ tr{!}{!};
 my @i_diffs = do {
   my $i = 0;
   map   $_->[1],
   grep  $_->[0] eq '!',
   map   [ $_, $i++ ],
   split '',
   $diff;
   };
 print qq{differing positions: @i_diffs};
"
!!=!!=!!
number of differences: 6
differing positions: 0 1 3 4 6 7

[download]
Updates:
  1. Found GrandFather's reply: Re: match and mismatch.
  2. Changed example to actually count and report positions of differing characters per OPer's request.

In reply to Re: How do i do a direct comparison of an array of strings? by AnomalousMonk
in thread How do i do a direct comparison of an array of strings? by Anonymous Monk

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