my @list = (1, 2, 3, 6, 9, 10, 13, 22, 20, 19, 15, 21);

printf "<=>: %s\n", join ",", sort { $a <=> $b } @list;
printf "cmp: %s\n", join ",", sort { $a cmp $b } @list;
printf "   : %s\n", join ",", sort @list;

##</code><code>##

<=>: 1,2,3,6,9,10,13,15,19,20,21,22
cmp: 1,10,13,15,19,2,20,21,22,3,6,9
   : 1,10,13,15,19,2,20,21,22,3,6,9