Actually im underwhelmed by it :( which is sad.
they chose to use some specific, static operators so that you can do interesting things with the data, instead of having it simplify your request to what you "probably" want.
I understand your point: and I would have figured it out. But this is marketed as an everydfay search engine - which it's not, it's an advanced search for an encyclopedia :)
i imagine if it turns out to be a common problem, they'll probably give you a little reminder message about it. "if you're looking for data comparison, use vs. instead of /"
In general its best to thing of that input field as a API with a huge syntax space, rather than something that is actually "understanding" anything. Getting the side-by-side comparisons can be done in many ways, like just using a comma instead of /
(edited, no need for "vs.", just series seems to do the trick)