Why don't you create tag handlers for "thread" and "node" that build up your hierachy?
Here something to get you started
#!/usr/bin/perl
use strict;
use warnings;
use XML::Twig;
use Data::Dumper;
my %result;
my $thread= new XML::Twig(
twig_handlers => {
thread => \&thread,
node => \&node,
}
);
$thread->safe_parse(join('',<DATA>));
print Dumper( \%result );
sub thread {
$result{$_->{'att'}->{'id'}}= childrenhash($_->children( 'node' ))
+;
}
sub node {
$_->set_att( structure => { $_->{'att'}->{'id'}, childrenhash($_->
+children( 'node' ))} );
}
sub childrenhash {
my %result;
foreach my $child (@_) {
my $ch= $child->{'att'}->{'structure'};
@result{keys %$ch}= values %$ch;
}
return \%result;
}
__DATA__
<?xml version="1.0" encoding="ISO-8859-1"?>
<thread id="504929">
<node id="504941">
</node>
<node id="504942">
<node id="504950">
<node id="504964">
</node>
</node>
<node id="504953">
</node>
</node>
<node id="504944">
</node>
</thread>
s$$([},&%#}/&/]+}%&{})*;#$&&s&&$^X.($'^"%]=\&(|?*{%
+.+=%;.#_}\&"^"-+%*).}%:##%}={~=~:.")&e&&s""`$''`"e