#  snip

     dependencies   =>
           {  # If A is "N", make list of inputs required
              "A" => {
                   N =>  [ qw/
                          admin_contact_fk                                        
                          tech_contact_fk
                          billing_contact_fk
                         / ],
                     }
     },
     constraints => {  # check these inputs with these subs
                 dn_id       => 'OK_int',
                 foo         => 'OK_chars',
     },

#  snip