This works for Moar, Parrot and JVM: $ perl6 -e 'printf("%.50f", 1.115)' 1.11500000000000000000000000000000000000000000000000
I added a test to S32-str/sprintf.t with the following commit: https://github.com/perl6/roast/commit/46ef5bf0e9. I'm closing the ticket.