until -package:numeric-prelude -package:base-prelude -package:distribution-opensuse -package:extra -package:rebase -package:elerea -package:faktory -package:github -package:Cabal-syntax -package:base-compat package:dunai
Similar to Yampa's delayed switching. Loses a b in case of an
exception.
Run the first
msf until the second one produces
True
from the output of the first.