...clipped... (not applicable)
#I was computing the intersection and not the union.

##</code><code>##

my @unique = do{
		my %seen;
		undef @seen{@list1, @list2, @list3};
		sort keys %seen;};

##</code><code>##

package ListMerger;
use strict;

sub new
{
	my $pkg = shift;
	my $self;
	return bless \$self, $pkg;
}
#call with references to lists as arguments
#ex: @union = $obj->union(\@list1,\@list2,\@list3);
sub union
{
	my $self = shift;
	my @lists = map{@{$_}}@_;
	return do{
		my %seen;
		undef @seen{@lists};
		sort keys %seen;
	};
}
#call with references to lists as arguments
sub intersection
{
	my $self = shift;
	my @lists = map{@{$_}}@_;
	my $list_count = scalar(@_);
	return do{my %seen;
        	$seen{$_}++ for(@lists);
        	map{delete $seen{$_} if($seen{$_}<$list_count)}keys %seen;
        	sort keys %seen;
        };
}
#call with references to lists as arguments
sub exclusion
{
	my $self = shift;
	my @lists = map{@{$_}}@_;
	my $list_count = scalar(@_);
	return do{my %seen;
        	$seen{$_}++ for(@lists);
        	map{delete $seen{$_} if($seen{$_} == $list_count)}keys %seen;
        	sort keys %seen;
        };
}
#call with references to list as arguments
sub shared
{
	my $self = shift;
	my @lists = map{@{$_}}@_;
	return do{my %seen;
		$seen{$_}++ for(@lists);
		map{delete $seen{$_} if($seen{$_} == 1)}keys %seen;
		sort keys %seen;
	};
}
1;