How do I add wildcard (i.e. *) to any search string by default?

I notice that when I search a certain string at drupaldocs.org, wildcards (i.e. *) will be automatically added before and after the string. In this way, the search results will be improved dramatically. This is especially useful for drupal sites in Chinese, Korean and Japanese languages which do not have a space between characters and words. So I am wondering how can I hack the search module to include wildcards before and after any inputed search string? Thanks a lot!