[Bioperl-l] how to stop prerequisite modules auto-installing

[Joel Martin]

Hello,
   I went to test bioperl-live and Build.PL started updating
modules in my perl install w/o prompting me, frightening!  I
really need to test modules and other groups here need to
test them before they're updated so we don't break anything
when some module's api changes.

   I did svn co of bioperl-live then

perl Build.PL PREFIX=/scratch/bioperl-live

saw some output including
"I think you ran Build.PL directly, so will use CPAN to install prerequisites on demand"

then it went to cpan and tried updating Data::Stag in 
my perl install.

How can I ask it to prompt me before updating modules ( so
I can put the updated versions somewhere for it to find
that isn't the live perl install )?  Should I be running 
Build.PL indirectly?

Joel