#id   layer/first   layer/second
id1   value1         value2
id2   value3         value4

##</code><code>##


#!/usr/bin/perl -w

use strict;
use Data::Dumper;

my $list1 = "this/is/a/twig";
my $list2 = "this/is/a/branch";
my $list3 = "this/is/another/branch";

my $hash = {};
my $hashroot = $hash;
my @hashtags1 = split(/\//, $list1);
my @hashtags2 = split(/\//, $list2);
my @hashtags3 = split(/\//, $list3);

attach_leaf($hash,\@hashtags1, "leaf1");
attach_leaf($hash,\@hashtags2, "leaf2");
attach_leaf($hash,\@hashtags3, "leaf3");

print Dumper($hashroot);

sub attach_leaf{
	my ($tree, $branch, $leaf) = @_;

	# Work along the branch
	for(my $i = 0; $i < scalar(@$branch); $i++) { 
		# build branch
		if($i != (scalar(@$branch) - 1)){
			# build new branch if it doesn't exist already
			$tree->{$$branch[$i]} = {} if(! exists $tree->{$$branch[$i]}); 
			$tree = $tree->{$$branch[$i]};
		}
		# attach leaf
		else{
			$tree->{$$branch[$i]} = $leaf;
			return $hash;
		}
	}
}

##</code><code>##


$VAR1 = {
          'this' => {
                      'is' => {
                                'a' => {
                                         'branch' => 'leaf2',
                                         'twig' => 'leaf1'
                                       },
                                'another' => {
                                               'branch' => 'leaf3'
                                             }
                              }
                    }
        };