On Feb 7, 8:18     

> Where's the point of the rescue clause?      
> later, i.e. after the method has returned.

Why would the error show later? It is just so one could pass a
immutable, like 0 to #with without raising an error b/c it doesn't
respond to #dup.

> Also, as Tom pointed out, this is not the same as what I proposed - not
> even similar.

It's not?

  Hash.with([])

is not the same as

  Hash.with_arrays

?