Not exactly a solution perhaps, but I'm able to build Pugs from the darcs repository on Windows XP. Running dmake on the generated Makefile gives:

Skip blib\lib\Perl6\sync.pl (unchanged)
cp lib/Perl6/Pugs.pm blib\lib\Perl6\Pugs.pm
Skip C:\dev\fun\pugs\blib6\lib\Kwid.pm (unchanged)
cp lib/perlkwid.kwid C:\dev\fun\pugs\blib6\lib\perlkwid.kwid
dmake.exe:  Error -- `C:\dev\fun\pugs\blib6\script\kwid' not found, an
+d can't be made
dmake.exe:  Error code 255, while making 'subdirs'
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Uncommenting the lines:

#subdirs ::
#    $(NOECHO)cd ext\Kwid && $(MAKE) -f $(FIRST_MAKEFILE) all $(PASTHR
+U)
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and

clean_subdirs :
#    -cd ext\Kwid && $(TEST_F) $(FIRST_MAKEFILE) && $(MAKE) clean
    -cd ext\Pugs-MakeMaker && $(TEST_F) $(FIRST_MAKEFILE) && $(MAKE) c
+lean
    -cd ext\Test && $(TEST_F) $(FIRST_MAKEFILE) && $(MAKE) clean
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lets me build Pugs. I haven't looked into the Makefile.PL to try and solve this, but MakeMaker makes my eyes water, so I think I'll leave it manipulating the generated Makefile ... I'm using ghc 6.2.2, dmake and fetch the code with darcs pull. At least it's possible ;)