my @numericUnion = union{ $_[0] == $_[1] } [1,2,3], [2,3,4], [9]; #returns ( 1, 2, 3, 4, 9 ) 

my @stringUnion = union{ $_[0] eq $_[1] } [ qw( aaa bbb ccc ) ], [ qw( bbb ccc ddd ) ]; #returns( 'aaa','bbb','ccc','ddd' ) 

 my @unique = union{ $_[0]->isSameNode } [ qw( list of xml nodes ) ], [ qw( othrer list of xml nodes ) ] #unique node list


sub union(&@){
	my $eq = shift;
	@_ == 1 ? @{ $_[0] } :
	union(
		$eq, [
			@{ $_[0] },
			grep &{sub{
				!grep $eq->( $_, $_[0] ), @_[1..$#_]
			}}( $_, @{ $_[0] } ), @{ $_[1] }
		], @_[2..$#_]
	)
}