is it prime?

[Anonymous Monk]

hi all i wrote this function to check if the number is prime or not but i just want to confirm if i'm doing this correctly :

sub isPrime($) {
    $num = shift;
    my ($i,$c);
    for ($i = 1; $i < $num / 2; $i++)
    {
        if ($num % $i == 0){$c += 1;}
    }
    if ($c == 1){return 1;}
    return 0;
}