Dear monks,

I'm getting myself a bit confused. I have three arrays of values, all I want to do is get a list of those values that appear in any two of the arrays (not all three). 

1) array1:  1,2,5,9,11,12,13
2) array2:  1,2,5,11,12,13
3) array3:  1,2,5,7,9,12,13

[download]
Therefore, get numbers 9 and 11 only as they appear in two of the arrays.

I have so far maganged to find those that appear in all arrays but am not sure how to adapt my code to get those that appear in two arrays only.

Hope someone can advise me! 

my %union1;
my %isect1;
                                                                      
+                                    
# FIND THINGS THAT ARE IN BOTH ARRAY1 AND AND ARRAY2

foreach my $e (@array1)  { $union1{$e}=1}
foreach my $g (@array2) {
        if ($union1{$g}) { $isect1{$g}=1}
        $union1{$g}=1;
}
                                                                      
+                                    
my @isect1=keys %isect1;

# FIND THINGS THAT ARE IN ALL THREE ARRAYS
my %union2;
my %isect2;
                                                                      
+                                    
                                                                      
+                                    
foreach my $e (@isect1)  { $union2{$e}=1}
foreach my $g (@array3) {
        if ($union2{$g}) { $isect2{$g}=1}
        $union2{$g}=1;
}
                                                                      
+                                    
# @ISECT2 CONTAINS COMMON VALUES IN ALL THREE ARRAYS
                                                                      
+                                    
my @isect2=keys %isect2;

[download]

In reply to array comparison question by Anonymous Monk

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