Data strucure: Message ID (Parent)

-- 1 (0)
   |-- 2 (1)
   \-- 3 (1)
       |-- 4 (3)
       |   \-- 6 (4)
       \-- 5 (3)

##</code><code>##

# Get the data and store it in a message hash
while (<DATA>) {
    chomp(my ($id,$thread,$from,$date,$content) = split /,/);

    %{$msg->{$id}} = (
        thread  => $thread,
        from    => $from,
        date    => $date,
        content => $content
    );
}

##</code><code>##

foreach my $id (keys %{$msg}) {
    next if ($msg->{$id}->{thread} == 0);
    push @{ $msg->{ $msg->{$id}->{thread} }->{children} }, $id;
}