#!/usr/local/bin/perl
#!/usr/bin/perl
use strict;
use warnings;

sub union(\@\@){
  my ($ar, $br) = @_;
  my %union;
  $union{$_}++ for (@$ar, @$br);
  return keys %union;
}

sub intersection(\@\@){
  my ($ar, $br) = @_;
  my (%union, %intersection);
  $union{$_}++ && $intersection{$_}++ for (@$ar, @$br);
  return keys %intersection;
}

my @a = qw/0 1 2 3 4 5 6 7 8 9/;
my @b = qw/0 2 4 6 8 10 12 14 16 18/;
local ($, , $\) = (",", "\n");  # to pretty-print
print intersection(@a, @b);
print union(@a, @b);