Thomas wrote me today and said "hey, I rewrote the MacPerl built-in editor, you want it?" Yes, yes, I do.
I think our plan will be to release MacPerl 5.6.1 soon (a few weeks tops), and then put together MacPerl 5.6.2[ab]1, which will include the new editor stuff, along with any other new features we may deem appropriate. Bugfixes will go into 5.6.1 after that, but any new work will go into 5.6.2. Hopefully when perl 5.8.0 is released, perl 5.6.2 (a maintenance release) will be finalized and we'll release MacPerl 5.6.2 with the new editor.
Then work will commence on 5.8.0, which might get spread out over more time than it needs, but there's no rush; we just got 5.6.1/2 done!