AppSupport.framework contains a class called CPRegularExpression, which performs regular expression matching. Here is an interface and some sample code.
However, I strongly recommend against using this class. Why? Because the backend of CPRegularExpression is in fact regexec. regexec is underpowered and not fast at all (for commonly encountered regexes, at least). Combined with the dynamic nature of Objective-C it means very slow (you can get an IMP to speed this up though). Instead, you should use the more powerful and faster PCRE (it's of course hard to use, but there're plenty of wrappers).