I was not able to reproduce the anomalies,

Okay.

1. First problem: Your version of the generator is not -- for the same setting of srand-- producing the same randomly generated tree.

   At first, I assumed this must be because you were using a different rand to me. I guessed you might be running on some flavour of *nix -- but then I noticed your use of notepad above -- which squashed that idea.

   Then I thought you might be running some other flavour of windows perl -- perhaps Strawberry. So, I thought I'd re-generate the failing test cases using my version of the generator and supply you with the generated trees.

2. Second problem: my version of the generator is no longer producing the same trees for a given value of -S=nnn!

   Did I change the generator between posting and now? I don't remember, but I can only assume that something in the original code I used, that used rand has changed.

   Never mind: I'll reverse engineer the output I posted back to a raw tree structure and give you that.

3. Third problem: Reverse engineering this pretty form of output is extremely painstaking, laborious and painful!

   But I did it!

   <Reveal this spoiler or all spoilers in this node or all in this thread>

   Which fed to your dumper produces the same (malformed) dump that I originally posted:

   C:\test>anonBinTreeDumper.pl
       _____________________________/\___________________________________
   +___________________________________________________
     _/\___________________                                              
   +               ___________________________________/\
    /\           _________/\_______                     _________________
   +______________/\_______________________________    Z
   a b     _____/\_______    _____/\               ____/\________________
   +_____                          _______________/\_
         _/\___    _____/\  /\_    q           ___/\      _______________
   +____/\_______            _____/\_               /\
        /\   _/\  /\_    l m  /\_            _/\_ _/     /\___           
   +         ___/\   _______/\___   /\_________    X Y
       c d  /\ g h  /\_      n  /\     _____/\  //\     1   _/\___       
   +       _/\_  G  /\_____    _/\ P         _/\_
           e f     i  /\       o p    /\___  v wyxz        /\   _/\______
   +_     /\  /\   H   ___/\  /\ O       ___/\  /\
                     j k             r   _/\              2 3  /\   _____
   +/\_  C D E F      /\_  L M N       _/\_  U V W
                                        /\ u                  4 5  /\_   
   +  /\             I  /\            /\  /\
                                       s t                        6  /\_ 
   + A B               J K           Q R S T
                                                                    7  /\
                                                                      8 9
   [download]

   But that raises another problem...

4. Fourth problem: if you look at the raw tree above, you'll see it is malformed: [['y','z'],]; the x,y node is paired with a null node.

   And that raises the final problem.

5. Fifth problem: Given that the raw tree is reproduced from the pretty-printer output, there is no way to determine if the tree my generator fed your dumper was malformed; or if the malformation is a result of occlusion in the dumper output?

   I don't think that it is possible for the generator to produce bad trees -- but I haven't proven that.

   Looking at the spacing between the 'z' and the '1' nodes, the gap is too big, which makes me think it is a artifact of the dumper.

At that point, I manually made the simplest correction to the raw tree that (I thought) would make it valid:

and re-ran the dumper. As you can see, it still produces the identical, malformed dump:

C:\test>anonBinTreeDumper.pl
    _____________________________/\___________________________________
+___________________________________________________
  _/\___________________                                              
+               ___________________________________/\
 /\           _________/\_______                     _________________
+______________/\_______________________________    Z
a b     _____/\_______    _____/\               ____/\________________
+_____                          _______________/\_
      _/\___    _____/\  /\_    q           ___/\      _______________
+____/\_______            _____/\_               /\
     /\   _/\  /\_    l m  /\_            _/\_ _/     /\___           
+         ___/\   _______/\___   /\_________    X Y
    c d  /\ g h  /\_      n  /\     _____/\  //\     1   _/\___       
+       _/\_  G  /\_____    _/\ P         _/\_
        e f     i  /\       o p    /\___  v wyxz        /\   _/\______
+_     /\  /\   H   ___/\  /\ O       ___/\  /\
                  j k             r   _/\              2 3  /\   _____
+/\_  C D E F      /\_  L M N       _/\_  U V W
                                     /\ u                  4 5  /\_   
+  /\             I  /\            /\  /\
                                    s t                        6  /\_ 
+ A B               J K           Q R S T
                                                                 7  /\
                                                                   8 9
[download]

So then I fed that corrected tree to my dumper:

C:\test>perl \perl64\site\lib\Tree\Dump.pm
                  ____________________________________________________
+_________________________________
    _____________/                                                    
+                                 \___________________
  _/             \_________                                 __________
+_________________________________/                   \
 / \        _____/         \_____                   _______/          
+                                 \_______________    Z
 a b    ___/     \_____   _/     \            _____/       \__________
+___________                   ___/               \_
      _/   \_   _/     \ / \_    q          _/     \    ___/          
+           \___       _______/   \_________      / \
     / \  _/ \ / \_    l m / \_         ___/ \_   _/   /   \___       
+          _/   \  ___/       \_  /         \_    X Y
     c d / \ g h / \_      n / \    ___/   \ / \ / \   1  _/   \___   
+        _/ \_  G /   \___   _/ \ P      ___/ \_
         e f     i / \       o p   /   \_  v w x y z     / \  _/   \__
+___    / \ / \   H  _/   \ / \ O      _/   \ / \
                   j k             r  _/ \               2 3 / \  _/  
+   \_  C D E F     / \_  L M N      _/ \_  U V W
                                     / \ u                   4 5 / \_ 
+   / \             I / \           / \ / \
                                     s t                         6 / \
+_  A B               J K           Q R S T
                                                                   7 /
+ \
                                                                     8
+ 9
[download]

At this point, I'm kicking the ball into your court to decide if it is worth pursuing further?