$_ == ($num1 +4) will only ever be true once at most; if $num2 is small enough, it will never be true.

Given the number of times "%" (the modulo operator) has been mentioned in this thread, I'm surprised you haven't looked into it. [follow the link I've provided for details of this operator]

To produce a newline after every 5 numbers, you'll need to change

print "\n" if ( $_ == ($num1 +4) );
[download]

to something like

print "\n" unless ($_ - $num1 + 1) % 5;
[download]

You may need to sit down with paper and pencil to understand why this code works. That would probably be time well spent.