{
   my $iter = get_target_iter($stuff);

   while (my (
      $env_name,
      $platform_name,
      $host_name,
      $target_name,
      $total_capacity,
      $free_capacity,
   ) = $iter->()) {
      local $, = "\t";
      local $\ = "\n";

      print $env_name,
            $platform_name,
            $host_name,
            $target_name,
            $total_capacity,
            $free_capacity;
   }
}

##</code><code>##

sub get_target_iter {
   my ($envs,  
          $env_name,
          $platforms,
             $platform_name,
             $hosts,
                $host_name,
                $targets,
                   $target_name,
                   $total_capacity,
                   $free_capacity   );
                      
   my (@envs, @platforms, @hosts, @targets);

   my $level;

   $envs = $_[0];
   @envs = keys %$envs;
   $level = 0;

   return sub {
      for (;;) {
         if ($level == -1) {
            return;
         }

         if ($level == 0) {
            if (@envs) {
               $env_name = shift(@envs);
               $platforms = $envs->{$env_name};
               @platforms = keys %$platforms;
               ++$level;
            } else {
               --$level;
               redo;
            }
         }
         
         if ($level == 1) {
            if (@platforms) {
               $platform_name = shift(@platforms);
               $hosts = $platforms->{$platform_name};
               @hosts = keys %$hosts;
               ++$level;
            } else {
               --$level;
               redo;
            }
         }
         
         if ($level == 2) {
            if (@hosts) {
               $host_name = shift(@hosts);
               $targets = $hosts->{$host_name};
               @targets = keys %$targets;
               ++$level;
            } else {
               --$level;
               redo;
            }
         }
         
         if ($level == 3) {
            if (@targets) {
               $target_name = shift(@targets);
               my $target = $targets->{$target_name};
               $total_capacity = $target->{total_capacity};
               $free_capacity  = $target->{free_capacity};
            } else {
               --$level;
               redo;
            }
         }

         return $env_name,
                $platform_name,
                $host_name,
                $target_name,
                $total_capacity,
                $free_capacity;
      }      
   }; 
}

##</code><code>##

use Algorithm::Loops qw( NestedLoops );

sub get_target_iter {
   my ($envs) = @_;
   
   my $iter = NestedLoops(
      [
               [ keys %$envs                          ]  ,
         sub { [ keys %{$envs->{$_[0]}              } ] },
         sub { [ keys %{$envs->{$_[0]}{$_[1]}       } ] },
         sub { [ keys %{$envs->{$_[0]}{$_[1]}{$_[2]}} ] },
      ],
   );
   
   return sub {
      if (my (
         $env_name,
         $platform_name,
         $host_name,
         $target_name,
      ) = $iter->()) {
         my $target = $envs->{$env_name     }
                             {$platform_name}
                             {$host_name    }
                             {$target_name  };
         my $total_capacity = $target->{total_capacity};
         my $free_capacity  = $target->{free_capacity};

         return $env_name,
                $platform_name,
                $host_name,
                $target_name,
                $total_capacity,
                $free_capacity;
      }

      return;
   };
}