~/s/m/build > cat test.sh
    #!/bin/sh
    echo $(case x in x) echo foo;; esac)
    ~/s/m/build > mrsh -n test.sh
    program
    program
    └─command_list ─ pipeline
      └─simple_command
        ├─name ─ word_string [2:1 → 2:5] echo
        └─argument 1 ─ word_command ─ program
          └─command_list ─ pipeline
            └─case_clause
              ├─word ─ word_string [2:13 → 2:14] x
              └─items
                └─case_item
                  ├─patterns
                  │ └─word_string [2:18 → 2:19] x
                  └─body
                    └─command_list ─ pipeline
                      └─simple_command
                        ├─name ─ word_string [2:21 → 2:25] echo
                        └─argument 1 ─ word_string [2:26 → 2:29] foo