until -package:numeric-prelude -package:base-prelude -package:distribution-opensuse -package:Cabal -package:protolude -package:foundation -package:classy-prelude -package:hosc -package:basic-prelude package:dunai -is:exact
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.