Dear NateTut,
This module doesn't compute the exact Hamming Distance as I required.
Instead it returns edit distance. Here is the example:

perl -MText::LevenshteinXS -e '
$s1 = 'GGAAG'; 
$s2 = 'GAAGA'; 
$diff = distance($s1,$s2); 
print "$diff\n";'
[download]

It prints: 2 instead of 3.