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To be honest, i would not want that kind of behavior. I, and only i am to decide if a new package is installed on my machine.
Using a good documentation along with your program, and anyone familiar using cpan should be able to deal with it.
If only by the fact that i rather use the deb / rpm packages (if they exist) in the standard linux distribution i use, than a self compiled one.
All system upgrades take care of new packages as well then for me.
Don't mess with auto installation.
For perl-only packages, well, just put them in your program library.
"We all agree on the necessity of compromise. We just can't agree on when it's necessary to compromise." - Larry Wall.