Sorting numbers

The problem with sort's default behaviour is that it sorts alphabetically. Here's snippet that incorrectly sorts numbers:

my @numbers = (20,1,10,2);
my @incorrectly_sorted_numbers=sort @numbers;
print "\n\nNumbers, incorrectly sorted\n";
print join "\n",@incorrectly_sorted_numbers;

Here's the output of this Perl script. Probably not what was intended.

1
10
2
20

If you want to have the numbers sorted by their value, you need use the <=> (aka Spaceship Operator):

my @numbers = (20,1,10,2);
my @correctly_sorted_numbers = sort {$a <=> $b} @numbers;
print "\n\nNumbers, correctly sorted\n";
print join "\n",@correctly_sorted_numbers;

The variables $a and $b are automatically set by Perl. The output is now:

1
2
10
20