[Haskell-beginners] "sleep" in Haskell

[Michael Mossey]

I can't find a "sleep" function in Haskell. This relates to my wish to use 
PortMidi and control the timing of actions. Maybe there is another way to 
do this sort of thing in Haskell. Can anyone help, either with PortMidi or 
just a general explanation of how IO operations could be placed at certain 
points in time?

Thanks,
Mike