Map each array into a hash and test for the existence of the value.

my %array1 = map {$_ => $_}(1,2,5,9,11,12,13);
my %array2 = map {$_ => $_}(1,2,5,11,12,13);
my %array3 = map {$_ => $_}(1,2,5,7,9,12,13);

my %all = map {$_=>$_} (keys %array1, keys %array2, keys %array3);

foreach (sort {$a <=> $b} keys %all)
{
    if (exists($array1{$_}) + exists($array2{$_}) + exists($array3{$_}
+) == 2)
    {
        print "$_\n";
    }
}
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