code: private function validateRequiredParameters()
      {
          $ret = true;
          foreach ($this->parameterCluster->prefixes as $prefix => $parameters) {
              foreach ($parameters as $parameterClosure) {
                  if ($parameterClosure->required) {
                      if (! in_array(
                          $parameterClosure
                          ->prefix.
                          $parameterClosure
                          ->parameterName,
                          $this->argv
                      )) {
                          $aliasFound = false;
                          foreach ($parameterClosure->aliases as $prefix => $alias) {
                              if (in_array($prefix.$alias, $this->argv)) {
                                  $aliasFound = true;
                                  break;
                              }
                          }
                          if (! $aliasFound) {
                              $ret = $parameterClosure;
                              break 2;
                          }
                      }
                  }
              }
          }
  
          return $ret;
      }
docs: Validates the parameter list by verifying that it contains
  all required parameters. Returns the ParameterClosure if a parameter
  is missing, else it will return true.
  
  @return mixed