I think it means that the Makefile that was created (when you ran 'perl Makefile.PL') was written for some flavour of make *other* than 'nmake'. Running perl -V:make will tell you the flavour of make for which the makefile was written. You should either run that flavour of make, or do as Anonymous Monk did and specify that you want an "nmake flavoured" makefile by starting with perl Makefile.PL make=nmake.