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It would be interesting to see someone who understood both this and Perl 6's grammars to do a comparison. Based on Colm's quick description and my rough understanding of Perl 6 grammars, they sound like they are roughly equally powerful. But I admit I'm not sure I understand what "transformation language" means...

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Although similar in expressive power, Colm offers instruction logging to auto-reverse global state changes upon backtracking, something Perl 6 grammars does not (yet) support; at the moment we need to manually manage them with embedded blocks.

Thanks!

Re: "reverse global state changes upon backtracking": this sounds similar to the (manual) "undo actions" supported by the Kelbt parser [1], perhaps unsurprisingly as it was developed by the same author :-)

[1] http://www.complang.org/kelbt/

If they are then I don't deserve to be called "Dr. Thurston!"

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