What can be documented?
What is the difference between a question and a topic?
A hello world topic should consist of the most basic, complete, runnable, starter program available, that may be achieved by the widest amount of versions of the language, framework or system being documented. If necessary, the remarks should include basic instructions on how to prepare and execute the examples.
The topic should generally not require more than one or two examples, except in cases where later versions of the language are not backwards compatible. Remember, the hello world topic will be the starting point for anyone just beginning to learn a language. As such it should demonstrate minimum working examples that a learner can use to achieve a correct program. It is not necessarily a place to demonstrate a language's newest features.