You might also want to take a look at the
CPANPLUS module. It has a compatibility mode for CPAN.pm, plus it does a whole lot more like automatically reporting test to
CPAN testers. The docs mention that it is scheduled to take over CPAN.pm's duties in 5.10 so the time spent learning anything new will not be wasted.
And it's invoked nearly identically to CPAN:
perl -MCPANPLUS -e 'shell'