list_modules_and_pods.pl

#!/usr/bin/env perl
use strict;
use warnings;

use File::Find;
use File::Spec;

my %modules = ();
for my $path (grep { $_ ne '.' } @INC) {
    find(+{
        wanted => sub {
            my $name = $File::Find::fullname;
            return unless length($name) > length($path);
            return unless index($name, $path) == 0;
            return unless $name =~ s/\.(?:pm|pod)\z//;

            $name = substr $name, length($path);
            my @dirs = grep { ! /\W/ } File::Spec->splitdir($name);
            my $module = join('::', @dirs[1 .. $#dirs]);
            $modules{$module}++ if $module;
        },
        follow => 1,
        follow_skip => 2,
    }, $path);
}
print "$_\n" for sort keys %modules;

list_modules_by_cpan.pl

#!/usr/bin/env perl
use strict;
use warnings;

use CPAN;

my @results = ();
for my $module ($CPAN::META->all_objects('CPAN::Module')) {
    push @results, $module->id if $module->inst_version;
}
print join "\n", sort @results;