My other posts in this thread show that I am now starting all over again with a virgin installation, but have the same problem.

I have not installed a new version of ExtUtils::MakeMaker. It looks like the version I have is 6.56.

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

---------- MAKEMAKER.PM
our $VERSION = '6.56';
[download]

That subroutine in MM_Win32.pm is identical to the one you've shown (but I added line numbers).

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 }
[download]

And my Perl make configvar seems to point at dmake.

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