#!/usr/local/bin/perl
use strict; use warnings; $| = 1;
use Vi::QuickFix;

use Algorithm::Graphs::TransitiveClosure qw( floyd_warshall);

my %graph;
my %nodes;
while (<DATA>) {
    my @next = split;
    @nodes{ @next} = ();
    while ( @next > 1 ) {
        # build refexive and symmetric relation
        my $top = shift @next;
        my $below = $next[ 0];
        $graph{ $top}->{ $top} = 1;
        $graph{ $top}->{ $below} = 1;
        $graph{ $below}->{ $top} = 1;
    }
}

# build transitive closure
floyd_warshall( \ %graph);

# pull off chains
my @chains;
while ( keys %nodes ) {
    my $node = each %nodes;
    my @chain = sort { $a <=> $b } keys %{ $graph{ $node} };
    push @chains, \ @chain;
    delete @nodes{ @chain};
}

print "@$_\n" for sort { $a->[ 0] <=> $b->[ 0] } @chains;
exit;

__DATA__
  1     27
  1     32
  1     68
...