標準入力を読むなら

(load "~/quicklisp/setup.lisp")

(let* ((*standard-output* (make-broadcast-stream))
       (*error-output* *standard-output*))
  (ql:quickload :series))

(use-package :series)

(write-string
 (collect 'string (scan-stream *standard-input* #'read-char)))

yarn:~% echo "hello\nworld" | sbcl --script /tmp/a.lisp
hello
world