if the code is passed as eval it works fine. I assume here is because ! is used to define metadata inside a st file.��

Yes, I'd guess that you are triggering the !! delimited reading when you give a .st. In short, giving a .st file as an argument triggers a FileIn operation, not an execute smalltalk script.

It just happens that FileIn is an executable format (sort of), so you can use it as a script engine until you reach such issues.

Thierry