NSRegularExpression: Replace url text with tags

I am currently using a UIWebView to stylize posts from twitter. Some tweets of course contain URL's, but do not contain the tags. I am able to pull out the URL, however I am not sure how to add the tags and place back into the tweet. I will then use the same approach here to add links to the @usernames and #hashtags. Here is an example of my current code:

NSString *tweet = @"Sync your files to your Google Docs with a folder on your desktop.  Like Dropbox.  Good choice, Google storage is cheap. http://ow.ly/4OaOo";

NSRegularExpression *expression = [NSRegularExpression regularExpressionWithPattern:@"(?i)\\b((?:[a-z][\\w-]+:(?:/{1,3}|[a-z0-9%])|www\\d{0,3}[.]|[a-z0-9.\\-]+[.][a-z]{2,4}/)(?:[^\\s()<>]+|\\(([^\\s()<>]+|(\\([^\\s()<>]+\\)))*\\))+(?:\\(([^\\s()<>]+|(\\([^\\s()<>]+\\)))*\\)|[^\\s`!()\\[\\]{};:'\".,<>?«»“”‘’]))" options:NSRegularExpressionCaseInsensitive error:NULL];

NSString *match = [tweet substringWithRange:[expression rangeOfFirstMatchInString:tweet options:NSMatchingCompleted range:NSMakeRange(0, [tweet length])]];
NSLog(@"%@", match);// == http://ow.ly/4OaOo

Ultimately, I would like the final string to look like this:

Sync your files to your Google Docs with a folder on your desktop. Like Dropbox. Good choice, Google storage is cheap.