UTF-8 and PCRE

Hello! I would appreciate if anybody could tell me how to use an utf8 encoded string in a regular expression. I have tried this $string = "a username written in greek letters"; preg_match('#^[\w][\w0-9_]{2,39}$#', $string); Which does not work, i have also tried to utf8_decode the string and pass it to the regex, which doesn't work either. I would appreciate if anybody could help me out here, i have searched the web but with no results. Thanks a lot in advance, Jürgen Hauser