Another minor clarification.
Import more classes.
1. Improved grouping of results in the output.

2. Fixed a parsing bug for matrices using semicolons.  Previously, it didn't group the rows and instead flattened them.

3. Added tagging of a number elements in the output.  This makes it possible to inspect the ParseResults object and figure out what kind of construct it represents.

4. Added some debugging scaffolding.

5. Added support for a -d options on the command line, to drop you into the Python debugger.