Had occasion to do some perl stuff recently. I forgot how cpanm builds and tests everything during install of modules. I don't think this is really needed behavior in this case and is out of line with other language packages installers (pip, gem). Besides, there's a huge speed improvement from this tiny change.
Here's an example using: `time cpanm Mason`
w/o --notest (current)
w --notest (in PR)
That's worth it for me.