until -package:numeric-prelude -package:base-prelude -package:distribution-opensuse -package:Cabal -package:base -package:snap-core -package:foundation -package:base-compat -package:monad-loops 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.