use 5.010;
use strict;

sub isPrime (_)
{
	my $num = shift;
	for my $div (2 .. sqrt $num)     # start at 2, end at sqrt($n)
	{
		return if $num % $div == 0;  # return false if $n evenly divides
	}
	return 1;  # return true if we got through the entire loop
}

for (1 .. 30)
{
	if (isPrime)
	{
		say "$_ is prime";
	}
	else
	{
		say;
	}
}