Grazie mille per l'aiuto!

Un'altra cosa che non capisco di quello script è come funziona il commento in alto che cambia a seconda del numero di cookie che hai;
codice:
	var str='';	if (Cookies<5) str='You feel like making cookies.<br>But nobody wants to eat your cookies.';
	else if (Cookies<25) str='Your cookies are popular<br>with your dog.';
	else if (Cookies<50) str='Your cookies are popular<br>with your family.';
	else if (Cookies<100) str='Your cookies are popular<br>in the neighborhood.';
	else if (Cookies<500) str='Your cookies are renowned<br>in the whole town!';
	else if (Cookies<2000) str='Your cookies are worth<br>a lot of money.';
	else if (Cookies<5000) str='Your cookies bring<br>all the boys to the yard.';
	else if (Cookies<10000) str='People come from very far away<br>to get a taste of your cookies.';
	else if (Cookies<17000) str='Kings and queens from all over the world<br>are enjoying your cookies.';
	else if (Cookies<30000) str='Your cookies have been named<br>a part of the world wonders.';
	else if (Cookies<60000) str='Your cookies have been placed<br>under government surveillance.';
	else if (Cookies<100000) str='The whole planet is<br>enjoying your cookies!';
	else if (Cookies<150000) str='Creatures from neighboring planets<br>wish to try your cookies.';
	else if (Cookies<250000) str='Elder gods from the whole cosmos<br>have awoken to taste your cookies.';
	else if (Cookies<400000) str='Your cookies have achieved sentience.';
	else if (Cookies<1000000) str='The universe has now turned into<br>cookie dough, to the molecular level.';
	else if (Cookies<1000000000) str='A local news station runs<br>a 10-minute segment about your cookies. Success!<br><span style="font-size:50%;">(you win a cookie)</span>';
	else str='it\'s time to stop playing<br><span style="font-size:50%;">(more fun milestones in the next update I promise)</span>';
	l('comment').innerHTML=str;
Oltre ad aver dichiarato la variabile Cookies; per far comparire la scritta devo scrivere nell'html il testo comment che verrà sostituito con il valore str?? saresti così gentile da farmi un esempio?