#!/usr/bin/perl

while (<>) {
    chop;
    s/-//g; # remove all dashes
    tr/x/X/;
    @array = split("");
    $sum = 0;

    for ($i = 0; $i <= $#array; $i++) {
        if ($array[$i] eq "X") {
            $array[$i] = 10;
        }
        $sum += ($i+1) * $array[$i];
    }
    printf "Checksum is %d\n", $sum%11;
}