operator: words-to-list

    description:
        words-to-list ket
        splits the given ket on ', ' and ' and '
        it is the inverse of list-to-words

    examples:
        words-to-list |a, b, c, d and e>
            |a> + |b> + |c> + |d> + |e>
    
        -- demonstration of inverse property:
        list-to-words words-to-list |a, b, c, d and e>
            |a, b, c, d and e>
    
        -- implemented using split/ssplit:
        split[" and "] split[", "] |a, b, c, d and e>
            |a> + |b> + |c> + |d> + |e>

        ssplit[" and "] ssplit[", "] |a, b, c, d and e>
            |a> . |b> . |c> . |d> . |e>

    see also:
      list-to-words, split, ssplit