If in you I'd remove completely any mention to cpanm for win32 users
Odd, I rarely have troubles when using cpanm on win32 (in fact, it's the only CPAN client I use on Windows). But it is true that I never bother to cpanm --self-upgrade : I cannot think of a time since 5.010 where I really thought "I need to upgrade my cpanm client". Maybe I'm the exception in that regard.
And I see the mixed matchsticks, too, but it hasn't seemed to bother cpanm for me:
C:\> where cpanm
c:\usr\local\apps\berrybrew\perls\system\perl\bin\cpanm
c:\usr\local\apps\berrybrew\perls\system\perl\bin\cpanm.bat
C:\> cpanm --version
cpanm (App::cpanminus) version 1.7044 (c:\usr\local\apps\berrybrew\per
+ls\system\perl\bin/cpanm)
perl version 5.030000 (c:\usr\local\apps\berrybrew\perls\system\perl\b
+in\perl.exe)
...
C:\> c:\usr\local\apps\berrybrew\perls\system\perl\bin/cpanm --version
cpanm (App::cpanminus) version 1.7044 (c:\usr\local\apps\berrybrew\per
+ls\system\perl\bin/cpanm)
perl version 5.030000 (c:\usr\local\apps\berrybrew\perls\system\perl\b
+in\perl.exe)
...
(in fact, as shown, it doesn't bother cmd.exe, either)