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;

    }