Indeed, the module is buggy. The comment here helped unbreak a script I wrote using the module. The lines that need to be commented are:

# in distance()
        foreach my $i (1 .. $n) {
            #if ($i != $n && substr($s,$i) eq substr($t,$i)) {
            #    push @result,$i;next;
            #}
            $d[$i][0]=$i;
        }
        foreach my $j (1 .. $m) {
            #if ($j != $m && substr($s,$j) eq substr($t,$j)) {
            #    push @result,$j;next;
            #}
            $d[0][$j]=$j;
        }

# and the two early returns in fastdistance()
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