I appreciate your input but...

I did look at Test::Harness and found:

  The global variable $Test::Harness::switches is exportable and can be used
  to set perl command line options used for running the test script(s). The
  default value is `-w'.

which I don't think is going to do what I want it to do.  My
understanding is that $Test::Harness::switches = "-w blah" would
result in

  perl -w blah t/test.t

not

  perl -w t/test.t blah  < this is what I want

Also, I want to set a variable in Makefile.PL that will set
a variable in Makefile to be used by make test.