To answer my own question (finally), the reason the last line of the loop "does nothing" is because thats the way I designed it! The list already contains all the lower-case alpha's, so trying to add more will do nothing! D'oh!

Of course, what I had intended to do was (0 == int(rand 4)) and $fifo1->( chr(65+rand 26) ); but I just couldn't see it!