Further to the hint in haukex's post: The bitwise-xor of equal length strings (update: assumed to be ASCII strings; see sundialsvc4's point here++) is a neat differencing trick. Here's an example that extracts zero-based offsets of differing characters:
c:\@Work\Perl\monks>perl -wMstrict -le
"my ($x, $y, $z) = qw(TTTATTT TTTTTTT TBTTTTT);
;;
for my $ar ([ $x, $y ], [ $x, $z ], [ $y, $z ], ) {
my ($p, $q) = @$ar;
my $d = $p ^ $q;
my @offsets;
push @offsets, $+[0]-1 while $d =~ m{ \G \x00* [^\x00] }xmsg;
print $p;
print $q;
if (@offsets) {
printf qq{diff(s) at offset(s) %s \n}, join q{, }, @offsets;
}
else {
print qq{no diffs \n};
}
}
"
TTTATTT
TTTTTTT
diff(s) at offset(s) 3
TTTATTT
TBTTTTT
diff(s) at offset(s) 1, 3
TTTTTTT
TBTTTTT
diff(s) at offset(s) 1
BTW: I, too, find your OP a bit vague.
Update: Arrrgh! Use m{ [^\x00] }xmsg instead of m{ \G \x00* [^\x00] }xmsg (simpler == better).
Double Arrrgh! Even simpler: Instead of
push @offsets, $+[0]-1 while $d =~ m{ [^\x00] }xmsg;
use
push @offsets, $-[0] while $d =~ m{ [^\x00] }xmsg;
(See perlvar for @+ and @- regex special variables.)
Give a man a fish: <%-{-{-{-<