Actually, you don't even have to bother with the  tr stuff if you only want the differing positions: 
>perl -wMstrict -le
"my ($x, $y) = qw{abXcdYef pqXrsYtu};
 my @i_diffs = differing_positions($x, $y);
 print 'number of differences: ', scalar @i_diffs;
 print qq{differing positions: @i_diffs};
 sub differing_positions {
   my $i = 0;
   map   $_->[1],
   grep  $_->[0] ne qq{\x00},
   map   [ $_, $i++ ],
   split '',
   $_[0] ^ $_[1]
   ;
   }
"
number of differences: 6
differing positions: 0 1 3 4 6 7

[download]

In reply to Re^2: 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

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.