keymaps

(define-prefix-command 'custom-map)
(global-set-key "\M-n" 'custom-map)
(define-key custom-map "\M-e" 'custom1)
(define-key custom-map "\M-r" 'custom2)

custom-map
=> (keymap
    (27 keymap
        (114 . custom2)
        (101 . custom1)))