1. Clean up the code in _insert. There is too much redundancy, and much
can be factored out.
Has been improved in v0.03 

2. Tree equivalencies. Currently, /contend/ /content/ /resend/ /resent/
produces (?:conten[dt]|resend[dt]) but it is possible to produce
(?:cont|res)en[dt] if one can spot the common tail nodes (and walk back
the equivalent paths).

3. Investigate how (?>foo) works. Can it be applied?

4. Investigate how to note which original pattern triggered the match
Coming along nicely: found a bug in perl (#32840)

5. Devel::Coverage testing to ensure all code paths are exercised. More
testing.

6. Factor out slide procedure.

7. Allow pretty-printed multiline RE output

8. _scan_node and _reduce_node are too computationally expensive.

