For the record...
The regex-posix package also failed to build for me with GHC 6.12.1 on
Windows with Cygwin due to >> undefined reference to `_impure_ptr' <<
Again this builds fine with MinGW once you have the GNU regex library
installed (its not installed as a default MSys package). With a
runhaskell Setup.hs ... install you need to set the
extra-include-dirs to pick up regex.h and the extra-lib-dir to pick up
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