} elsif ($difference == 13) { $checkdigit = '/';
} elsif ($difference == 14) { $checkdigit = '.';
} elsif ($difference == 15) { $checkdigit = '+';
- } elsif ($difference == 16) { $checkdigit = 'A';
- } elsif ($difference == 17) { $checkdigit = 'B';
- } elsif ($difference == 18) { $checkdigit = 'C';
- } elsif ($difference == 19) { $checkdigit = 'D';
} else { die "error calculating checkdigit";
}