... is there a perlVar or function that is the TRUE array of hash key ... that,when changed, changes the keys ...

Others have answered this in the negative and explained why it can't be done. In support, consider that a hash (or associative array) key is an index of the array. Would you expect that in a positional array @ra there would be some way to directly operate on the index of element $ra[1] (i.e., 1) to change it to, say, 42 and expect the element to change its position in the array correspondingly? I suppose this kind operation is conceivable, but the fact that it doesn't exist in any language (AFAIK) suggests its inutility. (Update: I'd be interested to know if there's a language with an operator like this for either type of array.)