Man pages sections > man3 > Algorithm::CheckDigits::M23_002

# CheckDigits::M23_002 - compute check digits for VAT Registration Number (IE)

 CheckDigits::M23_002(3pm) User Contributed Perl Documentation CheckDigits::M23_002(3pm)

## NAME

CheckDigits::M23_002 - compute check digits for VAT Registration Number (IE)

## SYNOPSIS

```  use Algorithm::CheckDigits;
\$dni = CheckDigits('ustid_ie');
if (\$dni->is_valid('8473625E')) {
# do something
}
\$cn = \$dni->complete('8473625');
# \$cn = '8473625E'
\$cd = \$dni->checkdigit('8473625E');
# \$cd = 'E'
\$bn = \$dni->basenumber('8473625E');
# \$bn = '8473625'
```

## DESCRIPTION

### ALGORITHM

1.
Beginning right all digits are weighted with their position in the number (i.e. the number left from the check digit is multiplied with 2, the next with 3 and so on).
2.
3.
The check digit is the sum from step 2 modulo 23. This number is expressed as the corresponding letter from the alphabet where A-V correspond to 1-22 and W stands for check digit 0.

### METHODS

is_valid(\$number)
Returns true only if \$number consists solely of numbers and the last digit is a valid check digit according to the algorithm given above.

Returns false otherwise,
complete(\$number)
The check digit for \$number is computed and concatenated to the end of \$number.

Returns the complete number with check digit or '' if \$number does not consist solely of digits and spaces.
basenumber(\$number)
Returns the basenumber of \$number if \$number has a valid check digit.

Return '' otherwise.
checkdigit(\$number)
Returns the checkdigit of \$number if \$number has a valid check digit.

Return '' otherwise.

None by default.