Some may say Ruby is a bad rip-off of Lisp or Smalltalk, and I admit that. But it is nicer to ordinary people.

Now that is a demotivator. But Ruby must be evolving, and that quote may be outdated. So I have thought of a question to the Ruby-lovers, that may help me make up my mind to take the time to learn it. One of the best Scheme macros is, in my opinion, and-let*, from the SRFI-2. How would one write the following in Ruby, a procedure that I wrote a couple of nights ago?

;; Tries to get session from current request
(define (get-session request)
  (and-let* ((cookies (request-cookies request))
             (p (assoc "session_id" cookies))
             (sid-str (cdr p))
             (sid (string->number sid-str))
             ((integer? sid))
             ((exact? sid))
             (sp (assq sid *sessions*)))
    (cdr sp)))

In the and-let* macro, the clauses are evaluated and the variables are bound sequentially, creating new scopes for the next expressions. If any of the forms evaluates to #f (false in Scheme), the computation is aborted, no other expressions are evaluated, and the whole form evaluates to #f. How would I write this in concise Ruby?