#!/usr/bin/perl -w

use strict;
use warnings;

my @array = map {[split / /]} (
	"11 12", "11 13", "9 8 7", "3 4", "11 4"
);

my %index = ();
for my $i (0..$#array) {
	for my $val (@{$array[$i]}) {
		push @{$index{$val}}, $i;
	}
}

for my $i (0..$#array) {
	my $arr = $array[$i] or next;
	$array[$i] = undef;

	my %values = ();
	for my $val (@$arr) {
		next if $values{$val}++;

		for my $ind (@{$index{$val}}) {
			my $related = $array[$ind] or next;
			$array[$ind] = undef;
			push @$arr, @$related;
		}
	}
	
	print join(' ', sort {$a <=> $b} keys %values), "\n";
}

##</code><code>##

3 4 11 12 13
7 8 9