I quite like this suggestion. If we flip the key, value around to make it inline with what forEach etc do, then we don't need the placeholder for iterating without the key:

    fast-each [value] from arr {

    }

    fast-each {value} from obj {

    }
 
    fast-each [value, key] from arr {

    }

    fast-each {value, key} from obj {

    }

The disadvantage is that this looks like array comprehension but isn't.

Alternative:

    fast-properties key, value from obj {

    }

    fast-elements index, value from arr {

    }

    fast-properties value from obj {

    }

    fast-elements value from arr {

    }