* Incorporate Grune/Jacobs point about inaccessibility/unproductivity interaction.

* Deal with the issue of trace file handle for a grammar that is deep-copied.  Fall back
  to STDERR, and allow override?

* Rename grammar when deep-copied.  Check that this works.

* Test these traces, to ensure tracing reform did not break them:
    TRACE_ITERATION_SEARCHES TRACE_ITERATION_CHANGES
    TRACE_EVALUATION_CHOICES TRACE_COMPLETIONS TRACE_ACTIONS
    TRACE_VALUES TRACE_PRIORITIES

* Ensure Parse::Marpa::Internal::This::grammar set wherever appropriate.

* Check version, semantics in grammar, for sourced grammars and
  for source grammar itself.

* Add right and left evaluation in rules

* Test proper and perl5 separation

* Speed-up for pre-computing lexables.  Grammar::LEXABLES, etc.

* Test (or remove?) lexing suffixes.

* Allow macros:
     @VALUE
     $VALUE_REF
     $VALUE[n]
     $VALUE{NAME}
     $VALUE{NAME}[n]
     @RULE
     $RULE_REF

* Add locations for earlemes.  Also for rules?  Use in Carp messages.

* Allow alternation.

* Allow compiled grammars (also, inplace option?)

* Add to test set
   - basic test for all branches of counted rules: matrix is
     keep/no-keep, separated yes/no, right/left,
     0-1, 1-1, 0-2, 0-5, 1-2, 1-5, 0-*, 1-*, 2-*, 5-*

* (Later) Look at Yacc macros yyerrok YYERROR YYACCEPT YYABORT YYRECOVERING.

* (Later) Look at error recovery.   Is anything in Parse::Yapp or yacc useful?
