cpanm installs ExtUtils::MakeMaker again and again on FreeBSD

anazawa has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks, App::cpanminus installs ExtUtils::MakeMaker again and again on FreeBSD:

$ uname -a
FreeBSD (host) 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Tue Jan  3 07:15 UT
+C 2012     root@obrian.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  
+i386
$ perl -v
This is perl 5, version 12, subversion 4 (v5.12.4) built for i386-free
+bsd-64int
$ su
# cpan App::cpanminus
# cpanm Moose
...
==> Found dependencies: ExtUtils::MakeMaker
...
Building and testing ExtUtils-MakeMaker-6.62 ... OK
..
# cpanm Moo
...
==> Found dependencies: ExtUtils::MakeMaker
...
Building and testing ExtUtils-MakeMaker-6.62 ... OK
...
[download]

I reported what happened to the CPAN author and the ports maintainer of devel/p5-App-cpanminus months ago. I wonder cpanm doesn't know which module is installed. And so I think the above problem depends on the platform, not cpanm itself. On the other hand, the cpan command works well. Why does cpanm install ExtUtils::MakeMaker again and again? Should I use 'cpan' instead of 'cpanm' on FreeBSD?

Update: added version of cpanm (Thanks to Anonymous Monk)

# cpanm -v
cpanm (App::cpanminus) 1.5007 on perl 5.012004 built for i386-freebsd-
+64int
Work directory is /root/.cpanm/work/1329665008.1924 ( <- Should I hide
+ this number here? )
You have make /usr/bin/make
You have LWP 6.03
You have /usr/bin/tar: bsdtar 2.8.4 - libarchive 2.8.4
You have /usr/bin/unzip
[download]

Update: The following works well: (Thanks to one of my followings on Twitter)

# cpanm --uninst-shadows ExtUtils::MakeMaker
# cpanm Mojolicious
[download]

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