I wonder if in Perl6 it will be more practical to attach the cached sort key to the item using a property, instead of making an array of tuples. That would prevent making copies of the data.

I also think that the behavior of ⍋ (\N{APL FUNCTIONAL SYMBOL DEL STYLE}, if that's not in your font) is somehow more primitive, and this ought to be available directly. More variations of sorting could be made using this than around our existing sort function.

—John