if its an array you can compare both in the following way

    @union = @intersection = @difference = ();
    %count = ();
        foreach $element (@a, @b) { $count{$element}++ }
        foreach $element (keys %count) {
        push @union, $element;
        push @{ $count{$element} > 1 ? \@intersection : \@difference }
+, $element;
        }

    foreach $int (@difference){
        if ($int ne " "){
            @fname = split(/ /, $int);
            print "\n difference elements --> $fname[0]\n";
        }
    }
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Edited by planetscape - added code tags