C:\Old_Data\perlp>perldoc -q intersection  
Found in C:\Perl64\lib\pods\perlfaq4.pod  
  How do I compute the difference of two arrays?  How do I compute the intersection of two arrays?  
    Use a hash. Here's code to do both and more. It assumes that each  
    element is unique in a given array:  
  
            @union = @intersection = @difference = ();  
            %count = ();  
            foreach $element (@array1, @array2) { $count{$element}++ }  
            foreach $element (keys %count) {  
                    push @union, $element;  
                    push @{ $count{$element} > 1 ? \@intersection : \@difference }, $element;  
                    }  
  
    Note that this is the *symmetric difference*, that is, all elements in  
    either A or in B but not in both. Think of it as an xor operation.  
  
  
C:\Old_Data\perlp>