Dear wise ones, I've seen a small number of posts in which new users are encouraged not to include a leading ampersand when calling their own user-written functions whose definitions share the same file. One such admonition went as far as saying not to include it "unless you know the difference between using it and not using it and are sure that what it does when you include it is really what you want". Yet I have not seen any explanation of what the difference is between including a leading ampersand and not including it. I've always used a leading ampersand when calling &my_function and have never noticed a problem. Why is the use of a leading ampersand discouraged? What is the difference between including one and not including one? Thank you.