Why cache_clear_all('string', 'cache_page', true) doesn't work?

I want to delete specifice pages in cache, note all page cache. The code is:

function hook_init() {
  cache_clear_all('string', 'cache_page', true);
}

It doesn't work.

If changing the code to

cache_clear_all();

It's ok, but deleted all cache in cache_page

The opened cache mode will cause AHAH in Drupal 5 abnormally, so it must delete AHAH page in cache