sentence --Operation, two inputs. Abbreviation: se
     The two inputs may be words or lists. The output is a list formed
     from the two inputs in this way: if either input is a word, that word
     becomes a member of the output list; if either input is a list, the
     members of that input become members of the output. Here are some
     examples:

          first input second input output
          "hello "test [hello test]
          "goodbye [cruel world] [goodbye cruel world]
          [a b] [c d] [a b c d]
          [] "garply [garply]

     If an input is the empty list, as in the last example above, it
     contributes nothing to the output.