use warnings;
use strict;
use Data::Dumper;

if ('1234' =~ /(?<A>1)(?<B>2)(?<A>3)(?<B>4)/) {
    print Dumper(\%-);
}

__END__

$VAR1 = {
          'A' => [
                   '1',
                   '3'
                 ],
          'B' => [
                   '2',
                   '4'
                 ]
        };