I agree with Laurent. And I could do with more sigil, which is more controversial. As much I would like to get rid of the € as a French currency, I would like to have it as sigil for types that are Associative, Positional and Scalar. Many kinds of tree nodes could have that property. In Perl 6, a match acts like it has these properties but can't advertise it with .^roles (see below). $/ would be written as €/. Ironically, a non match is Nil and not Match. And one successful match value cannot be used as an invocant to .^roles :

 'a' ~~ /a/; say $/.^roles 
 OUTPUT: «(exit code 1) Unexpected named argument 'transitive' passed
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