[Haskell-beginners] exercise 3.10 in YAHT

[George Huber]

I'm currently working through "Yet Another Haskell Tutorial" by  H. 
Daume and have a question on how to proceed with his exercise 3.10.

The exercise question is:  Write a program that will repeatedly ask the 
user for numbers until he types in zero, at which point it will tell him 
the sum of all the numbers, the product of all the numbers, and, for 
each number, its factorial.

The hint that is given is to write an IO action that reads a number and 
either returns an empty list (if the number is zero) or recurses itself 
making a list from the number and the result of the recursive call.

Daume presents and example of such a function:

askForWords = do
    putStrLn "Please enter a word:"
    word <- getLine
    if word == ""
        then return []
        else do
            rest <- askForWords
            return (word : rest)

so, based on his example I created the function:

getNums = do
    putStrLn "Enter a number (zero to stop):";
    strNum <- getLine
    let num = read strNum
    if num == 0
        then return []
        else do
            rest <- getNums
            return (num:rest)

loading the file that contains the above function into GHCi (version 
6.8.3) gives the following error "The last statement in a 'do' construct 
must be an expression"

being a beginner, I'm at a loss at the cause of the error and how to fix 
it -- any suggestions?

thanks,
george