OK, I'm going to assume a database design like the following. It's rather simplified, but it'll get the idea across.

Actors
------
A_ID           integer
A_Fullname     varchar

Episodes
--------
E_ID           integer
E_Title        varchar

Roles
-----
R_ID           integer
R_Name         varchar

Actor_Role_Ep
-------------
ARE_ID         integer
ARE_Actor_ID   FK References Actor(A_ID)
ARE_Episode_ID FK References Episode(E_ID)
ARE_Role_ID    FK References Role(R_ID)

Now, if you have some actors in multiple roles, or some roles played by multiple actors, your SQL statement will return multiple rows. So you should then loop through the results in a while loop. Example code below.

# I'm assuming a valid $dbh exists.

my $sql = $dbh->prepare_cached("
SELECT ARE_ID, A_Fullname, E_Title, R_Name
FROM   Actor_Role_Ep, Actor, Episode, Role
WHERE  ARE_Actor_ID   = A_ID
AND    ARE_Role_ID    = R_ID
AND    ARE_Episode_ID = E_ID
WHERE  (whatever you want here);");

$sql->execute();
# If you need to pass in information above, then put the variables inside the ()'s.

while (($are_id, $a_name, $e_title, $r_name) = $sql->fetchrow_array) {
  print "$a_name played $r_name in episode $e_title.\n";
}

I hope that helps you..