Programming challenge: wildcard exclusion in cartesian products

[wkehowski at cox.net]

When I run this I get through ghc I get

C:\Documents and Settings\User\My Documents\wildcard>ghc
"./wc-zielonka.hs"
compilation IS NOT required
C:/Languages/ghc/ghc-6.4.1/libHSrts.a(Main.o)(.text+0x1d):Main.c:
undefined refe
rence to `__stginit_ZCMain'
C:/Languages/ghc/ghc-6.4.1/libHSrts.a(Main.o)(.text+0x43):Main.c:
undefined refe
rence to `ZCMain_main_closure'
collect2: ld returned 1 exit status

Unless there's a command line option I'm missing?