libgnuregex is the regex subset of Gnulib, the GNU portability library. The
regex subset offers an extension of the regex(3) API to allow more flexibility
in the flavor of regular expressions. libgnuregex also enhances POSIX
regular expressions with more features and shorthand, such as:

- \b and \B (word boundary, not word boundary)
- \s and \S ([[:space:]], [^[:space:]])
- \w and \W ([[:alnum:]], [^[:alnum:]])
- \` and \' (beginning of subject, end of subject)

WWW: http://www.gnu.org/software/gnulib/