That's Algol/Pascal's equality operator, Erlang's inequality operator (Pascal used "<>") and Haskell's binding operator (or whatever it's actually named inside

That's Algol/Pascal's equality operator, Erlang's inequality operator (Pascal used "<>") and Haskell's binding operator (or whatever it's actually named inside the do-notation). In fact, Algol designer's considered using "<-" for assignment.