Chances are, if you've been reading Elm code older than a year, that you've seen a strange squiggly symbol
It used to be exposed by the Signal namespace, but was then obsoleted in favour of just using its full name
Signal.map (which is now itself obsolete).
in merge (dir <~ Keyboard.arrows) (dir <~ Keyboard.wasd)
in Signal.merge (Signal.map dir Keyboard.arrows) (Signal.map dir Keyboard.wasd)