Perl6 will have macros. Good. Cool. But, sadly, that seems to be close to the most specific thing anyone says about the subject. There is some further discussion in Apocalypse & Exegesis 6, but nothing in the Synopsis.
Now, considering that macros are a language feature and that the Synopses are presented as the language spec, I wonder if there shouldn't be something there. Exactly what, though, I won't pretend to know. :) -- Schwäche zeigen heißt verlieren; härte heißt regieren. - "Glas und Tränen", Megaherz