The parser behaves differently in scalar or list context, like with Perl 5.

Actually, no, unlike Perl 5 the Perl 6 parser has no clue about scalar vs list context, which is completely driven by run-time binding so that context can be lazy. The only place the parser appears to pay attention to this is in choosing how to parse assignment based on the form of the left side, but this is merely the application of a precedence limiter to the right side so that the operator precedence parser knows whether to stop at the next comma or not. The only semantic distinction that heavily influences parsing is whether a name is predeclared as a type or named value (in which case the parser will not look for function arguments), but this also is not related to run-time context.