Solution Review: Implement the Sieve of Eratosthenes

# Assume that $n is already defined
my @array = 2 .. $n; # Due to 0-based indexing, index of a number $p in this list is $p - 2.

# Implementing Sieve of Eratosthenes. We'll use 1 to cross-off.
foreach my $p (@array) {
    next if $p == 1; # Select the first non-1 element of the array
    foreach my $j ($p-1 .. $#array) { # Replaces all of its multiples with a 1
        $array[$j] = 1 if $array[$j] % $p == 0;
    }
}
 
# Counting the left over elements (non-1's). They must all be the primes.
my $count = 0;
for (@array) {
    $count++ unless $_ == 1;
}
 
print $count;