Same code doesnt work with ocamlc vs online editor

Learning
2

The trailing ; is the source of the syntax error, it makes the rest of your code reads as

let _  =
  add my_stack 3;
  let popped = pop my_stack in Printf.printf "%d\n" popped

The playground toplevel is then discarding this last incomplete sentence because you may complete it later whereas ocamlc has to fail on the incomplete sentence.

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