The following form, suggested by the book "Perl Best Practices" (ISBN 0596001738), is easy to understand and maintain. If speed is truly important, it should be a candidate in your benchmark. 
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;
}

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Bill

In reply to Re: Pattern Identification by BillKSmith
in thread Pattern Identification by WhiteTraveller

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