$ perl -MO=Deparse -e 'my @a = 0 .. 10; sort @a;'
my(@a) = (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
sort @a;

$ perl -MO=Deparse -e 'my @a = 0 .. 10; sort { $a cmp $b } @a;'
my(@a) = (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
sort @a;
[download]

So sort { $a cmp $b } @array is optimized away.

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated