With all options finally set and a medium-level interface developed, we can finish the definition and retrieve http://www.cliki.net/CFFI, as is done in the tutorial.
(defcfun "curl_easy_perform" curl-code (handle easy-handle))
cffi-user> (with-output-to-string (contents) (let ((*easy-write-procedure* (lambda (string) (write-string string contents)))) (declare (special *easy-write-procedure*)) (curl-easy-perform *easy-handle*))) => "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN\" .... Now fear, comprehensively</P> "
Of course, that itself is slightly unwieldy, so you may want to define a function around it that simply retrieves a URL. I will leave synthesis of all the relevant REPL forms presented thus far into a single function as an exercise for the reader.
The remaining sections of this tutorial explore some advanced features of CFFI; the definition of new types will receive special attention. Some of these features are essential for particular foreign function calls; some are very helpful when trying to develop a Lispy interface to C.