Building array from list

[william humphrey]

I was wondering. If you have a list:

apple,1
orange,1
grapefruit,1
tango,2
blue,3
green,3
yellow,3
zebra,9

And you want to convert it into an array:

(apple,orange,grapefruit[1])
(tango[2])
(blue,green,yellow[3])
(zebra,[9])

What would be the easiest way. I'm always a little confused by arrays but it
seems to me this should be a very simple and fast conversion. The array is
intentionally a string "apple,orange,grapefruit" that results from key [1]

Bill