@a = (1,5,3);;
@b = (5,2,1);;
@sortedIndices = sort{ $b[ $a ] <=> $b[ $b ] } 0 .. $#b;;

@a = @a[ @sortedIndices ];;
@b = @b[ @sortedIndices ];;

print "@a\n@b";;
3 5 1
1 2 5