Topaz

Topaz was Chip Salzenberg's attempt to reimplement Perl 5 in C++ in the late 1990s. Topaz was abandoned after the Coffee Mug Incident.

Sapphire

Simon Cozens tested around 2000 how to reimplement Perl.

Ponie

(Perl (5) On New Interpreter Engine) had aimed to implement the Perl 5 language on Parrot. It was developed 2003-2006 by Arthur Bergman and Nicholas Clark. Ponie had the potential to integrate Perl 6 and Perl 5 code in the same process. That would have been useful for language bootstrap purposes, and also to make lots of the Perl 5 based CPAN libraries available to Perl 6 users. Some thought at one point even it might become Perl 5.10.. It was discontinued because emulating all of the idiosyncracies of Perl 5 was daunting, and the developers were presumably daunted.