CAS command question

[parisse]

The CAS is coherent with itself, incompatibilites happens between HOME and CAS, and I'm afraid they can never totally disappear because the logic behind is not the same.
Programming with strings should only be used as a last resort solution, it's much more efficient to program with expressions (after having learned the minimum about how a CAS works, i.e. expression structure and evaluation).
You should explain what you mean with your wall comparison for those like me who are not from the US (or Mexico) and don't understand what you mean.