Drupal - hook_form_alter (How to redirect user when altering a form)

/**
 * Implementation of hook_form_alter().
 * Use these functions to alter the "charity" forms.
 */
function user_validator_form_charity_node_form_alter(&$form, &$form_state) {

  $form['bookverify'] = array(
      '#type' => 'fieldset',
      '#title' => t('Confirmation'),
      '#weight' => 20
    );
  $form['bookverify']['words'] = array(
      '#type' => 'textfield',
      '#title' => t('First five words from Lesson 12'),
      '#description' => t('To register for this website ...'),
      '#default_value' => '',
      '#maxlength' => 32,
      '#required' => TRUE,
      '#size' => 32,
    );
  $form['#validate'][] = 'user_validator_charity_validate';
  $form['#submit'][] = 'user_validator_charity_submit';

  # this works (redirection)
  $form['#redirect'] = 'charity-suggestion-thank-you';
}