use strict;
use warnings;
sub string_type {
    $_ = shift;
    my $type
        #         format             ?       type
        = /^\d{2}.\d{2}.\d{2}$/      ?  'date'
        : /^\d{2}.\d{2}.\d{4}$/      ?  'date'
        : /^[A-Z]{2}\d{9}[A-Z]{2}$/  ?  'Royal Mail Track & Trace code'
        : /^\d{16}$/                 ?  'visa card'
        : /^\d{13}$/                 ?  'EAN-13 barcode'
        :                               'unrecoginized string'
        ;
    if ($type eq 'EAN-13 barcode') {
        ... # Handle sub-types
    }
        
    return $type;
}