Maybe I skimmed too fast, but I thought the sorting of array_b was only a logical sort to show how array_a needed to be reordered.

If that's not the case, saving the indicies and using them twice would do the trick:

my @indicies = sort { $array_b[$a] <=> $array_b[$b] } 0..$#array_b;
my @sorted_a = @array_a[@indicies];
my @sorted_b = @array_b[@indicies];
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