Matching word boundaries in Text.Regexp

I would like to match word boundaries in a regular expression but this doesn't seem to work with Text.Regex in GHC 6.4.2. The regular expression looks something like: "\\b(send|receive)\\b" to match either the keyword send or the keyword receive but not the word sending. Neither works \< and \> for matching the beginning and end of a word. Thanks for any help, Bernd