Martin,
A couple of observations. Recent versions of Perl already have Digest::MD5
included ("in the core", as we say). I'm afraid I don't have the exact
definition of "recent" handy, but I think it was in the 5.8 time frame. If you
can run the following command without error, then you've got it:
$ perl -e "use Digest::MD5;"
$
If you do need to build it, running the Makefile.PL is only the first step in
building an extension. It just generates the description file for MMK or MMS.
A typical complete build and install sequence looks like:
$ perl Makefile.PL
$ MMK
$ MMK test
$ MMK install