How can we return multiple tag variables with proper binding?

At first we thought we needed this every time:

<let/count=0 />
<let/message="hello" />
<return={
    count,
    countChange(newCount) {
        count = newCount;
    }
    message,
    messageChange(newMessage) {
        message = newMessage;
    }
} />

Attribute tags to the rescue!

<let/count=0 />
<let/message="hello" />
<return>
    <@value count:=0 message:=message />
</return>

This looks pretty good in concise mode

let/count = 0
let/message = "hello"
return
    @value count:=0 message:=message

And it extends to `const`, which can be used in interesting ways

let/count = 0
const/counter
    @value count:=0 reset() { count = 0 }

button onClick:=counter
    -- ${counter.count}
button onClick=counter.reset
    -- Reset