New EEP draft: Pinning operator ^ in patterns

[Eugene]

> This is a cute feature, but it carries 
> a large cognitive cost and is not worth having compared to how 
> relatively little it is used.

it has literally zero cost, because it is OPTIONAL.
you want "old" behaviour you simply omit new feature.

in return, if you read a program and see this new notation
you immediately (without reading context) know that at this
certain mention this particular variable is UNbound or bound.
(i propose unbound, whereas original proposal was opposite)

the error reporting becomes more meaningful by
separating a massive subclass of "bad-matches"
as its own class: "already bound"
(in this regard the original proposal is
slightly more complex than my counter-proposal)