In this example, first two channels don't take a key, I /think/ you have to specify a key to separate them so the keys match to the 3rd and 4th channel. (I'm really not sure)

Code:
join #cake,#foobar,#waffles,#news a,a,waffles_password,news_password


Key:
#waffles == waffles_password
#news == news_password