my %h4;

         %h3
+--------------------+
|       +----------+ |
| k3 => | Ref ------------+
|       +----------+ |    |
+--------------------+    |
                          |
         %h4              |
+--------------------+    |
|                    |    |
|                    |    |
|                    |    |
+--------------------+    |
                          |
                          v
                         %h2
                +--------------------+
                |       +----------+ |
                | k2 => | Ref -----------+
                |       +----------+ |   |
                +--------------------+   |
                                         |
                                         v
                                        %h1
                               +--------------------+
                               |       +----------+ |
                               | k1 => | Str "v1" | |
                               |       +----------+ |
                               +--------------------+