As noted above the tests in S02-types/bool.t are passing for quite a while.
The only remaining problem was the segmentation fault with parrot when running '(0 but Bool::True) and print qq{$_ } for 1..1000;'. I just tested with the latest Rakudo Star (2015.02) and I was unable to reproduce the segfault there -- even with more iterations: $ perl6-p -e '(0 but Bool::True) and print qq{$_ } for 1..10000;' 1 2 [...] 10000 I'm closing this ticket as 'resolved'.