to
    => the recipient's address(es)
          This parameter may be either a comma separated list of email addresses or a reference to a list of addresses.

##</code><code>##

to => join(',',@rd_list);

##</code><code>##

@rd_list= ('a@b.com','b@b.com', 'c@c.com');

#Your example is then equivalent to:
$sender->MailFile(
{
    'to', 'a@b.com',
    'b@b.com', 'c@c.com'
    'subject', 'Test',
    'msg', "All,
  ...