At the risk of sounding redundant/irrelevant, thats called stemming. It brings any word into its "root" form. See http://www.comp.lancs.ac.uk/computing/research/ste mming/general/
Also, regex queries would be very difficult to implement on search engines (if not impossible), coz the nature of search is different. In every regex query, the pattern is the one which is pre-processed, while in search engines, the text is pre-processed. Because of the different nature of pre-processing involved, regex on search engines might not be possible.