Did you actually try my suggestions? Or, did you just read them and go "I don't get it."?

Yes, I tried your suggestions. I'm really interested in knowing how you would solve the problem, but with your indications I didn't get it:

Remove the no strict 'refs'; in both subroutines and try the following: ...

my $root = {};
_create_node ($root,"pp1","first");
_create_node ($root->{pp1},"ppp1","second");
_create_node ($root->{ppp1},"pppp1","third");
_create_node ($root->{pppp1},"ppppp1","root");

my $infos = _go_through('p1');
#my $infos = _go_through($root); # doesn't work either

print Dumper $infos;

sub _create_node
  {
#    no strict 'refs';
    my ($node,$parent,$node_info) = @_;
    @{$node}{qw/parent info/} = ($parent,$node_info);
  }

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

This doesn't work:

Obviously, I'm missing something, that is why I asked

citromatik

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. :-)

---

My criteria for good software:

1. Does it work?
2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

You need to adjust your syntax, try:

$node = $node->{"parent"};  ## Line 33
[download]

Update: this is incorrect, please ignore.