No need to use a word list literal in definition of ch-name; symbols will do:

  (defvarl ch-name (relate (rlist 0..32 127)
                           '(NUL SOH STX ETX EOT ENQ ACK BEL BS
                             HT LF VT FF CR SO SI DLE DC1 DC2 DC3
                             DC4 NAK SYN ETB CAN EM SUB ESC FS GS
                             RS US SPC DEL)
                           nil))