/**
 * Implements hook_block_view().
 *
 * Prepares the contents of the block.
 */
$myvariable = 'test';
function mymodule_subscribe_block_view($delta = '', $myvariable) {
  switch ($delta) {
    case 'mymodule_test':
      $block['subject'] = t('Test block');
      if (user_access('access content')) {
          // Pass data through theme function.
          $block['content'] = $myvariable;
      }
    return $block;
  }
}

function mymodule_subscribe_block_view($delta = '', $myvariable = 0) {
  switch ($delta) {
    case 'mymodule_test':
      $block['subject'] = t('Test block');
      if (user_access('access content')) {
          // Pass data through theme function.
          $block['content'] = $myvariable;
      }
    return $block;
  }
}