$hash = test::this(\%hash); 
for my $box (keys %{$hash}){ 
    print "this is box $box\n"; 
   for my $par (keys %{$hash{$box}}){ 
          
	   print "this is partition $par\n"; 
	   for my $sec (keys %{$hash->{$box}->{$par}}){
	    
	       print "this is section $sec\n"; 
	   } 
    }

}

##</code><code>##

sub this 
{
     
$temp = @_;
$Dbox = "Dbox";
$DDD = "DDD";
 $temp{"Dbox"}= "Dbox"; 
 $temp{Dbox}{$DDD}= "DDD";
for my $box (keys %temp){
     print "this is box $box\n"; 
    for my $par (keys %{$temp{$box}}){
    
	   print "this is partition $par\n"; 
	   for my $sec (keys %{$temp{$box}->{$par}}){ 
	   
	       print "this is section $sec\n"; 
	   }
    }

}

return \%temp;
}