perlbrew seems to ignore PERLBREW_ROOT

[tospo]

I just started to use perlbrew on an Ubuntu Precise installation and I guess I'm doing something wrong but can't figure it out.

I want to install my perls into a nfs mounted directory /software/lib/perl5/perlbrew
I set PERLBREW_ROOT to that directory and the two perl versions I installed so far have both correctly been installed there.
I also added export PERLBREW_ROOT=/software/lib/perl5/perlbrew to my .bashrc and I can confirm in a terminal that this is indeed set correctly.
In addition, perlbrew info also confirms that PERLBREW_ROOT is set to the above directory.

However, when I install a module like this

 perlbrew exec --with 5.14.2 cpanm Module::Build

It is successfully installed in my home directory under ${HOME}/lib/perl5 and I can't figure out why. Any clues what I might be doing wrong?
I can also confirm that the cpanm that is used appears to be the one installed with perlbrew (it's in the perlbrew path given above) Thanks for your help!

UPDATE
======
Turns out (thanks Corion) that it was an old .modulebuildrc file that had set the install_base to my home dir, so all modules based on Module::Build ended up there.

[tospo]

hmm, I have just seen that PERL5LIB isn't set at all but I'm not sure if that's the expected behaviour of perlbrew or should perlbrew have set it according to the perl version used?

[tospo]

another thing I just tested is the output of

$  perl "-V:install.*"

which confirms that "installprefix" is the /software/lib/perl5/perlbrew directoy for the perl version I have currently selected.
I read that cpanm installs modules in ${HOME}/lib/perl5 if it thinks that the current user has no permissions to install system-wide but I do have permissions on the directories under my perlbrew directory and I verified that I can write to them so I'm completely lost now what the problem might be.

[tospo]

It seems that this is a problem only with Module::Build.
I just tried to install something else (Text::CSV) and it installed in the /software path just as it should.
Unfortunately, half of CPAN depends on Module::Build and I just can't get it installed

[tospo]

actually, I guess it's a problem with everyting that uses Module::Build (which Text::CSV does't). I just tried to install Module::Info and that too ends up in my home directory.

[Corion]

In theory, Module::Build should respect whatever the current Perl tells it about module locations. Do you maybe have a leftover .modulebuildrc somewhere that screws up your configuration? Are there maybe Module::Build-specific environment variables?