OK, thx guys.
I do actually grok references (generally), but the bits of docs I was reading didn't clearly state the difference, ie that the 2nd method creates a ref to a new copy(!) of the array, as opposed to 1st method which creates a ref to the orig array..., they just talked about a ref to the array.
I suppose the results imply that, but it's nice to have it stated explicitly. It might have been a fortunate side-effect of something else I was missing.
Cheers
Chris