Oh. I see the problem and why I didn't see it before. Your problem is that you're mixing data structures. Try the following version of _create_node and _go_through:

_create_node ('p1',"pp1","first");
_create_node ('pp1',"ppp1","second");
_create_node ('ppp1',"pppp1","third");
_create_node ('pppp1',"ppppp1","root");

my $infos = _go_through('p1');
print Dumper $infos;

{
    my %nodes;
    sub _create_node {
        my ($node_id,$parent,$node_info) = @_;
        @{$nodes{$node_id}}{qw/parent info/} = ($parent,$node_info);
    }

    sub _go_through {
        my ($node_id) = @_;
        return "" unless defined ${$nodes{$node_id}}{"info"};
        my @info_nodes;
        while (${$nodes{$node_id}}{"info"} ne "root"){
            push @info_nodes, (${$nodes{$node_id}}{"info"});
            $node_id = ${$nodes{$node_id}}{"parent"};  ## Line 33
        }
        return \@info_nodes;
    }
}
[download]

I actually tested this code. :-)