C:\strawberry\perl\lib\ExtUtils
> find "our $VERSION" MakeMaker.pm

---------- MAKEMAKER.PM
our $VERSION = '6.56';

##</code><code>##

127 sub init_DIRFILESEP {
128     my($self) = shift;
129 
130     # The ^ makes sure its not interpreted as an escape in nmake
131     $self->{DIRFILESEP} = $self->is_make_type('nmake') ? '^\\' :
132                           $self->is_make_type('dmake') ? '\\\\'
133                                                        : '\\';
134 }

##</code><code>##

C:\strawberry\cpan\build
> perl -V:make
make='dmake';