Problem is, not all links start with http://. There are other protocols as well, and someone could forget the http://. Also, what if it's a link with arguments attached? That won't necessarily end with an alphanumeric character. URLs come in so many formats that it's really much better to just do like Perlmonks does and have links be marked by enclosing them in brackets. Either that or use a module specifically designed for finding URLs inside a block of text, but I wouldn't know where to look for one of those.