ChatAppend:
  type: world
  events:
    on player chats:
      - if <context.message.ends_with[--]>:
          - define message <context.message.before_last[--]>
          - flag <player> messages:->:<[message] >
          - narrate "You have <player.flag[messages].size> appended messages."
          - determine cancelled
      - else if <player.has_flag[messages]> && !<context.message.ends_with[--]>:
          - flag <player> messages:->:<context.message>
          - define appended_message <proc[CombineMessages].context[<player.flag[messages]>]><context.message>
          - flag <player> messages:!
          - determine <[appended_message]>

CombineMessages:
  type: procedure
  definitions: messages
  script:
    - define result <[messages]>
    - foreach <[messages]> as:message:
      - if <[message]> != <[messages]>:
        - define result <[result]><[message]>
    - determine <[result]>