That doesn't seem to work for me.

First, typing that in the shell gives me an error:

  zsh: no matches found: /(.*)/

So, I tried typing:

  cpan upgrade '/(.*)/'

Which at least kept my shell from trying to expand the last argument, but cpan complained:

  Warning: Cannot install upgrade, don't know what it is.
  Try the command

    i /upgrade/

  to find objects with matching identifiers.
  Sorry, install with a regular expression is only supported when unambiguous.
  Rejecting argument '/(.*)/'

So, instead at the shell I just typed:

  cpan

Then, at the cpan[1]> prompt, I typed:

  upgrade

That seemed to work.

Sorry meant the CPAN shell. Should have reproduced the prompt better. Also it does appear that the regex isn't required any longer. That's certainly nice.