Calling an external command from a Haskell program

[C.Reinke]

> If you want access to its I/O streams as well, you can use
> Posix.popen, which is not standard Haskell 98, I think, but it's
> in GHC.

Even worse, it is not portable (AFAICT)! I'm worried by the tendency
towards Posix, at a time when, e.g., GHC by default no longer
supports this on Windows (went missing in the move from cygwin to
mingw). Some also thought Posix overkill, and wanted a portable
replacement for the most-commonly-wanted functionality subset.. 

Could someone in the know please summarise the state of
Posix-support in Haskell implementations in general? 

I've cc-ed to the libraries list - perhaps someone there could
comment on the state of portable replacements for Posix
functionality, especially for popen and friends? I seem to
recall a very promising discussion about portable and flexible
ways to start subprocesses a while ago - has that led to any
concrete libraries?

Cheers,
Claus