OCaml's approach to semicolons is nice—they are clearly nothing more than sequence markers between side-effecting expressions.

    a ; b    (* a THEN       b *)
    a   b    (* a APPLIED TO b *)

You also can basically just desugar them to let bindings

    a ; b
    ==
    let _ = a in b

    a ; b ; c ; d e
    ==
    let _ = a in 
    let _ = b in
    let _ = c in
    d e

Due to static typing it's vanishingly unlikely that a forgotten semicolon will properly check.

    let this = x ; y (* if x : 'a       and y : 'b then this : 'b *)
    let this = x   y (* if x : 'a -> 'b and y : 'a then this : 'b *)

So forgetting a semicolon only check if `x` is an unapplied function of type `'a -> 'a` which the value you intended to completely ignore.