#!/usr/local/bin/perl

## Usage:
#   find_perl_dependencies.pl <DIR>
#

use strict;
use warnings;

use Module::Dependency::Indexer;
use Module::Dependency::Info;

my $start_dir = $ARGV[0] || '.';

Module::Dependency::Indexer::setIndex('/tmp/perl_dependencies.dat');
Module::Dependency::Indexer::makeIndex($start_dir);

my $dpidx = Module::Dependency::Info::retrieveIndex();
my $all   = $dpidx->{allobjects};

my @todo = map { @{ $all->{$_}->{depends_on} } }
  grep { exists $all->{$_}->{depends_on} }
  keys %$all;

my @modules;
my %seen;
while (my $pm = shift @todo) {
    next if $seen{$pm}++;

    push @modules, $pm;
    next unless exists $all->{$pm} and exists $all->{$pm}->{depends_on
+};

    my @reqs = grep { !$seen{$_} } @{ $all->{$pm}->{depends_on} };
    push @todo, @reqs;
}

print "$_\n" foreach sort @modules;
[download]

when run in a directory containing only this script:

% perl find_perl_dependencies.pl .
Module::Dependency::Indexer
Module::Dependency::Info
strict
warnings