I think what Randal L. Schwartz was referring to, when he said "cache it for the sort," was to use a very common sort optimization technique called, not coincidentally, the Schwartzian Transform.

@sorted =
    map { $_->[0] }
    sort { $a->[1] <=> $b->[1] }
    map { [ $_, (-s $_) ] }
    @unsorted;
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