init.el

;; I hope this works

(defun channel-names (channel)
  (when (erc-channel-p channel)
    (with-current-buffer channel
      (erc-get-channel-nickname-list))))

(defun intersect-lists (head &rest lists)
  "Intersect any number of lists"
  (if (consp lists)
      (let ((operand (car lists))
	    (rest (cdr lists)))
	(apply 'intersect-lists (intersection head operand) rest))
    head))