#!/usr/local/bin/perl

use strict;
use warnings;
use Data::Dumper;

my $hash = {};

while( my $line = <DATA> ) {
    chomp($line);

    $line =~ m/(\s*)(.*)/;
    my $level = int(length($1) / 2);
    my $caption = $2;

    my $node = { label => $caption,
                 children => []
               };
	
    if( $level == 0 ) {
        $hash = $node;
    }
    else {
        my $hash_item = $hash;
        for (1 .. ($level - 1)) {
            $hash_item = @{$hash_item->{children}}[scalar(@{$hash_item->{children}}) - 1];
        }

        push(@{$hash_item->{children}}, $node);
    }
}

print Dumper ($hash);

__DATA__
Building
  House
    Window
      Glas
        Silicium
    Door
    Roof
      Wood
  Hut
    Pizza
  Garage
    Door