Raku operator overloading

<5 0 10> literally constructs a List, a single List.

An analogy would be a list of things to do, a todo list. How many things is a todo list? It's 1 -- one todo list.

Thus you get the error message:

expected 3 arguments but got 1

What you want is to specify that you want one value that is itself made up of several values. Here's one way to do that:

sub circumfix:<α ω>( ( $a, $b, $c ) ) ...

The additional surrounding ( and ) cause destructuring.

D:\>6e "say <5 0 10>"
(5 0 10)

These aren't three arguments. It's a list of three values (of type IntStr) and therefore a single argument.