I wrote this to help me understand Abigail's code. I'd never seen the xor-string trick before.

#!perl
        
use strict;  
use warnings;
    
while (my $line=<DATA>) {
    chomp $line;   
    my ($f, $s) = split /\s+/,$line;
    unless (length ($f) == length ($s)) {
        print "\"$line\" -> $f-$s\n";
        next;
    }   
    if ($f == $s) {
        print "\"$line\" -> $f\n";
        next;
    }  

    my $first = join ' ',map {sprintf("%08b",ord)} ("$f" =~ /./g);
    print "$f\t= $first\n";

    my $second = join ' ',map {sprintf("%08b",ord)} ("$s" =~ /./g);
    print "$s\t= $second\n";
    
    my $xor = join ' ',map {sprintf("%08b",ord)} (("$f" ^ "$s") =~ /./
+g);
    print "XOR\t= $xor\n";

    my $index_of_first_diff = 0;
    $index_of_first_diff++ while($xor =~ /00000000 /g);

    print "Index\t= " , ' 'x9x$index_of_first_diff, "$index_of_first_d
+iff\n";

    print "Result\t= $f-", substr ($s, $index_of_first_diff), "\n\n";
}

__DATA__
324 329
325 349      
340 509
[download]

Output -

d:\>test.pl
324     = 00110011 00110010 00110100
329     = 00110011 00110010 00111001
XOR     = 00000000 00000000 00001101
Index   =                   2
Result = 324-9

325     = 00110011 00110010 00110101
349     = 00110011 00110100 00111001
XOR     = 00000000 00000110 00001100
Index   =          1
Result = 325-49

340     = 00110011 00110100 00110000
509     = 00110101 00110000 00111001
XOR     = 00000110 00000100 00001001
Index   = 0
Result = 340-509
[download]