[JadeNB]

> The `@` symbol is a variable by itself, what is very clear from it's name

I'm almost certain that this is false, at least in Perl 5. (Sigils are dramatically overhauled in Perl 6, and I haven't kept up.)

[lizmat → JadeNB]

<plug>

This blog post could be of interest: https://opensource.com/article/18/9/using-sigils-perl-6

</plug>

[JadeNB → lizmat]

In "What they have in common is that they consume the Callable role.", shouldn't 'consume' be 'perform' for consistency with your useage elsewhere?