sub unique { my %x; @x{@_} = @_; values %x }
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The reason to use values is that I need to get the unique set from an array of objects, not scalars. (This assumes, of course, that every object has a unique stringification. As I don't overload stringification in my objects, this works. If you do overload stringification ... good luck. Seriously.)

And, the reason for not using references is that I use this function as so:

my @final =
    map {
        # Something
    } unique grep {
        # Something
    } map {
        # Something
    } @start;
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