For a reliable cpan client, try dual-lived. It has no enviromental or setup problems and will report for the perl that you are using. For example:

#!/usr/bin/perl

use strict;
use warnings;

system("dual-lived namespace::autoclean -u");
system("dual-lived /^namespace::au/");
[download]

The -u in the first system call will either install or upgrade as necessary. Also, if you'd like a superfast namespace check of the whole "namespace" namespace, do:

#!/usr/bin/perl

use strict;
use warnings;

system("dual-lived /^namespace/");
[download]