<<< mml $${\phantom{\mathrm{fail}}\mathrm{k}}^2={\mathrm{k}}^2$$ >>> native [ ESuper (EGrouped [ EPhantom (EIdentifier "fail") , EIdentifier "k" ]) (ENumber "2") , ESymbol Rel "=" , ESuper (EIdentifier "k") (ENumber "2") ]