%h4 = %h3;

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