That paper cleared up most of my issues and it is amazing that it is
not amongst the papers that are referenced at the top of the the page
describing Control.Exception.
Anyway, there is one more problem I have related to exceptions that is
about forcing strictness. It relates to option parsing. I have an option -t
that says which track from a file of tracks to print. So I go

data Flags = TrackNumber !Int deriving(Read, Show, Eq)

makeTrackNumber :: String -> Flags
makeTrackNumber str =
    TrackNumber $ read str

options = [GetOpt.Option ['t'] ["tracknumber"] (GetOpt.ReqArg makeTrackNumber "tracknumber") "number of track to show"]

Now my main goes
main = do
  args <- getArgs
  opts <- evaluate $ GetOpt.getOpt GetOpt.RequireOrder options args
  print "done getting the opts"
  case opts of ...

which of course first prints "done getting opts" and then throws an exception if I give it a flag
-t abc. What would be the way to proceed here? Do I increase the strictness or do I write a handler
around my complete main? Even if I map the exception in makeTrackNumber to my very own
exception how do I find out which exact call gave a problem i.e. which is the call stack at the moment
the exception was thrown -- I might use makeTrackNumber in other contexts too.
Thanks in advance,
Immanuel