(defparameter +define-variable-label+ :define-variable)

(defmacro steroid-let (&rest forms)
  (flet ((filter-definitions (form-list &optional (definitions? t))
           (funcall (if definitions?
                      #'remove-if-not
                      #'remove-if)
                    (lambda (form)
                      (and (eq (first form) +define-variable-label+)
                           (= (length form) 3)))
                    form-list)))
    (let ((definitions (filter-definitions forms))
          (other-forms (filter-definitions forms nil)))
      `(let ,(map 'list #'rest definitions) ,@other-forms))))

;; Usage
(steroid-let
  (:define-variable x 2)
  (:define-variable c 1)
  (setf c (+ c x))
  (:define-variable y "asdf")
  (format t "~A: ~A~&" c y))