perl array, scalar and hash

#!/usr/bin/perl
use strict;
use warnings;

my @aa=("aa", "bb", "cc");
print "@aa\n";
my $aa_num=@aa;
print "$aa_num\n";

my %hash = ("a"=>1, "b"=>2,"c"=>3);
my @k = keys %hash;
print "@k\n";

print "OK\n" if keys %hash == $aa_num;

aa bb cc
3
c a b
OK