Brain fart? Actually using MakeMaker on DOS is a whole load easier. Here's the steps to a successful build if googling brings you this way:

C:\Users\mimi\swig\Examples\perl5\simple>type makefile.pl
use ExtUtils::MakeMaker;

WriteMakefile(
        NAME    => 'example',              # Name of package
        LIBS    => ['-lm'],                # Name of custom libraries
        OBJECT  => 'example.o example_wrap.o'  # Object files
);

C:\Users\mimi\swig\Examples\perl5\simple>perl makefile.pl
. . . 
C:\Users\mimi\swig\Examples\perl5\simple>dmake
. . . 
C:\Users\mimi\swig\Examples\perl5\simple>dmake install
. . . 
C:\Users\mimi\swig\Examples\perl5\simple>perl runme.pl
The gcd of 42 and 105 is 21
Foo = 3
Foo = 3.1415926
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