True, but then there are no guarentees that sort will produce consistant result if you do weird things with overload:

perl> use overload '""' => sub{ rand }, fallback => 1;;
perl> @n = map{ bless \$_ } 1 .. 10;;
perl> print $$_ for sort{ $a <=> $b } @n;;
10
9
8
4
5
3
7
6
2
1
perl> print $$_ for sort{ $b <=> $a } @n;;
10
5
4
6
3
9
7
8
1
2
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