[web2py] request.vars and lists question

[rick]

I have a simple function:

def simpletest(animals):
        theAnimals = request.vars["animals"]
        leng = len(theAnimals)
        return dict(leng = leng)

When I call it with two animals:
http://mySite.com/myApp/default/call/run/simpletest?animals=cat&animals=dog
.. I get the answer 2, as I would expect

When I call it with only one animal:
http://mySite.com/myApp/default/call/run/simpletest?animals=cat
.. I get the answer 3, the length of the string "cat"

I would prefer to get a list with only a single value, like ["cat"],
of length 1.
What could I do differently to make that happen?
Thank you,
rick