#!/usr/bin/perl -l

# http://perlmonks.org/?node_id=1174320

use strict;
use warnings;

my @answers;
my @queue = [[], [qw(2 6 5 7 4 3 9)]];

while( my $state = shift @queue )
  {
  my @have = $state->[0]->@*;
  my @more = $state->[1]->@*;
  if( @more )
    {
    @have == 0 || $have[-1] < $more[0] and
      push @queue, [[@have, $more[0]], [@more[1..$#more]]];
    push @queue, [[@have], [@more[1..$#more]]];
    }
  elsif( @have >= $#answers )
    {
    push @{$answers[@have]}, "@have";
    }
  }
print for $answers[-1]->@*;