A real Regular Expression engine. It's not a complete engine like the one Lex or Perl have, but it's a start.
People familiar with regexes know that there are more complicated forms than * and |. However, anything can be built from *, | and eps. For instance, x? (zero or one instance of x) is a shorthand for (x|eps). x+ (one or more instances of x) is a shorthand for xx*. The basis has been laid, the rest is just extensions.