use strict;
use warnings;

my (%posts, @threads, $id, $root, $board, $parent, $stamp, $title);

my @array;
while (<DATA>)
{
    chomp($_);
    my @subarray = split(/,/,$_);
    push @array, [@subarray];
}
my @sortedarray = sort { $a->[4] cmp $b->[4] } @array;

for my $x (0..$#sortedarray) {    
    ($id, $root, $board, $parent, $stamp, $title) = @{$sortedarray[$x]};
    my %post = ('id' => $id, 'root' => $root, 'parent' => $parent, 'stamp' => $stamp, 'title' => $title);
    $posts{$id} = \%post;
    if ($id == $parent) {
        push @threads, \%post;
    }
    else {
        push @{$posts{$parent}{'children'}}, \%post;
    }
}

construct($_) for @threads;
    
sub construct {
    my $p = $_[0];
    print  "$p->{'id'} $p->{'title'}\n";
    construct($_) for @{$p->{'children'}};
}

#id,board,root,parent,stamp,text
__DATA__
1,2,0,1,2006-01-02 08:15:00,test line 1 (first)
2,2,1,1,2006-01-02 08:16:00,test line 2 (second)
3,2,1,2,2006-01-02 08:21:00,test line 3 (third)
6,2,1,1,2006-01-02 08:23:00,test line 6 (seventh)
4,2,1,1,2006-01-02 08:22:00,test line 4 (sixth)
7,2,1,6,2006-01-02 08:25:00,test line 7 (eighth)
5,2,1,3,2006-01-02 08:23:00,test line 5 (fourth)
8,2,1,1,2006-01-02 08:17:00,test line 8 (fifth)