What kind of "interaction" are you intending to perform? There are a number of modules on CPAN that are OO, such as CGI.pm, DBI, or LWP and many others, and these can "interact" by definition, though not without some effort on the part of the programmer. Interaction between modules is usually by design, and as such, you can't really expect two modules written by two different people for two different purposes to interact spontaneously. They may be compatible, but it is in the program that you write where the interaction occurs.

A good example of interaction is the LWP system, the Web "browser" library for Perl. To implement this, there are a variety of objects which are used to represent everything from a server connection (HTTP::Request) through to a URL (URI), and many things inbetween. The library is very comprehensive, and highly abstracted, so if LWP is too confusing, you can always use LWP::Simple which makes it a snap to 'get' Web pages.

Perhaps some sample code would better illustrate this. This example grabs all the links from the Perl Monks page, something that HTML::LinkExtor does quite well, so this is for educational purposes only:

#!/usr/bin/perl -w

use strict;
use HTML::Parser;
use HTTP::Request;
use HTTP::Response;
use LWP::UserAgent;
use URI;

# Create a LWP::UserAgent object which can be used to fetch pages
my $agent = new LWP::UserAgent();

# Create a URI, which represents a location on the WWW
my $uri   = new URI ("http://www.perlmonks.com/");

# Create a HTML::Parser, used to process the HTML
my $parser = new HTML::Parser (
                        api_version => 3,
                        start_h     => [ \&Start, 'tagname,attr' ],
);

# Define a behavior, used by HTML::Parser when it encounters
# the "start" of a tag (i.e. a declaration like '<X>', where
# the tagname would be 'x', as it is always passed as lower-case)

sub Start
{
        my ($tagname,$attr) = @_;

        if ($tagname eq 'a')
        {
                print "$tagname href=$attr->{href}\n";
        }
}

# Make a download request for the page, which is requesting
# a 'GET' of the URL specified earlier
my $request  = new HTTP::Request ( GET => $uri->as_string() );

# Tell the LWP::UserAgent to process this request, and
# capture the response.
my $response = $agent->request ($request);

# Feed the response to the HTML::Parser, which because of
# the customized 'Start' function, will do something useful.
$parser->parse ($response->content());
[download]