Select document command for each major-mode

my-document.el

;; document
(defmacro major-mode-eql (mode)
  `(eql major-mode ,mode))

(defun my/man ()
  (interactive)
  (let* ((manual-program
         (cond
          ((or (major-mode-eql 'cperl-mode) (major-mode-eql 'perl-mode)) "perldoc")
          ((or (major-mode-eql  'python-mode) (major-mode-eql 'py-mode)) "pydoc")
          ((major-mode-eql 'ruby-mode) "ri")
          (t "man")))
        (prompt (format "%s entry: " manual-program))
        (input (read-string prompt)))
    (if (not (string= manual-program "man"))
        (manual-entry input)
      (man input))))

(global-set-key (kbd "<f1>") 'my/man)