the cpan shell can do it, so it should not be too difficult to lift that part out of the code and incorporate it into a cpansearch script.

Actually, it can be as easy as:

package main;
use strict;
use warnings;
use Modern::Perl;

use CPAN;

CPAN::HandleConfig->load;
CPAN::Shell::setup_output;
CPAN::Index->reload;

my $search = shift @ARGV;

my @modules = CPAN::Shell->expand("Module","/$search/");

say CPAN::Module::as_glimpse($_) for @modules;
1;
[download]

Add some option handling and argument checking and you are done!

Update: added an example script.