my @array1 = (1, 3, 4, 6);
my @array2 = (1, 2, 4, 6);
my @array3 = (1, 2, 3, 5);

my %seen;
my @union = grep { not $seen{$_}++ } (@array1, @array2);
	
undef %seen;
@union = grep { not $seen{$_}++ } (@union, @array3);

print join(' ', @union);

##</code><code>##

@array1 = (1, 2, 3, 4);
@array2 = (1, 3, 2, 4);