Not too hard, if the site already has some kind of a search engine, it can feed the URL to the search engine.

The safe thing to do is return a 404 with a few suggested links.

The problem is that "guessing" the intent of the URL will have unintended consequences. A URL will no longer be guaranteed to point to what you think it points to. This fundamentally breaks the assumption of what a URL is.

How could this happen?

1: Site creates article foo.com/chocolate_bars 2: Someone accidentally links to foo.com/cocoa_bars, which serves foo.com/chocolate_bars 3: Site creates article foo.com/coco_bars 4: Now foo.com/cocoa_bars serves foo.com/coco_bars