use List::Util qw( shuffle );
    my @letters = qw( a b c d e f g h i j k l m n o p q r s t u v w x y z
                      A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
                      0 1 2 3 4 5 6 7 8 9 );

    my @randoms;
    foreach my $x ( 0 .. 12 ) {
       push( @randoms, $letters[ int(rand(62)) ] );
    }

    return join('', shuffle(@randoms));