When collecting values into a list, if the first value collected uses (collect val :at :beginning),
and a subsequent value does not use the ":at :beginning" clause, then an error will occur:
"The value nil is not of type cons".
The following reproduces this error:
(iterate
(for i from 1 to 10)
(if (oddp i)
(collect i :at :beginning)
(collect i)))
