root
    => node1
    => node2
        => node2.1
        => node2.2
    => node3

##</code><code>##

    for (my $i=0; $i < $counter; $i++)
    {
        my $result = $sth->fetchrow_hashref ();
        # root node
        if (scalar @path == 0)
        {
            $offset = $result->{'lvl'} - 1;
            push @path, $result->{'payload'};
            push @tree, $result->{'payload'};
            next;
        }   
        # child node
        else
        {
            # going down (one step only)
            if (($result->{'lvl'} - $offset) > scalar @path)
            {
                my $last = $path[$#path];
                push @path, $result->{'payload'};
                push @{$tree[$#path][0]}, $result->{'payload'};
                $a_counter = 0;
            }
            # same level
            elsif (($result->{'lvl'} - $offset) == scalar @path)
            {
                my $last = $path[$#path -1];
                push @{$tree[$#path][$a_counter]}, $result->{'payload'};
                $a_counter++;
            }
            # going up
            else
            {
                my $steps = scalar @path - $result->{'lvl'} + ($offset -1);
                $#path = $steps;
                push @path, $result->{'payload'};
                my $last = $path[$#path];
                push @{$tree[$#path][0]}, $result->{'payload'};
                $a_counter = 0;
            }
        }