In “applicative” notation:
{{extern "manool.org.18/std/0.3/all"} in WriteLine[Out; "Hello world!"]}
OOPish notation (equivalent to the above, up to Abstract Syntax Tree):
{{extern "manool.org.18/std/0.3/all"} in Out.WriteLine["Hello world!"]}
LISPish notation (ditto):
{{extern "manool.org.18/std/0.3/all"} in {WriteLine Out "Hello world!"}}
Using a colon punctuator (ditto):
{{extern "manool.org.18/std/0.3/all"} in: WriteLine Out "Hello world!"}
Note that all semicolons, wherever allowed, are optional. The above example with all possible semicolons:
{{extern; "manool.org.18/std/0.3/all"} in: WriteLine; Out; "Hello world!"}