It seems you could do a great deal better by altering your approach a bit.

The method would go something like this... You start with a list of emails and you compare the first against all the rest, saving the list of distances. Sort your emails by their distance from the 'first' email. Then you sort of compress the list making further comparisons only between emails with similar distances from the original email.

This is based on the assumption that two emails which have dissimilar distances from a third can't themselves be similar. (I think this is a safe assumption with Text::Levenshtein, but I really don't have any experience with it.) If it is a safe assumption, you can probably approach a linear time solution.

-sauoq
"My two cents aren't worth a dime.";