SECTION_SIGN

A section sign (§) indicates where, in the parsing of a macro invocation, it should invoke one of its prefix functions. The order of section signs in the method name corresponds with the order of the prefix functions.

Prefix functions are passed all arguments that have been parsed so far. They can access a fiber-specific variable, SpecialAtom.CLIENT_DATA_GLOBAL_KEY, which allows manipulation of the current variables that are in scope, and also early parse rejection based on what has been parsed so far.