until -package:numeric-prelude -package:base-prelude -package:distribution-opensuse -package:extra -package:Cabal -package:intro -package:xmonad-contrib -package:rebase -package:ghc -package:conferer 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.