cpan2rpm Proc::Daemon /tmp/String-Canonical-1.2.tar.gz
To install from a URL:
cpan2rpm -i http://.../Proc-Daemon-0.03.tar.gz
To make a package out of the current directory (that contains a module):
cpan2rpm .
To create a list of packages stored in a file:
cpan2rpm -f module-list