{{
  : getDelimiter ( "-$ )
    getToken keepString cr ;
  : prepare      ( -$ )
    remapping off "" tempString ;
  : readLine     ( "-$ )
    10 accept tib ;
  : append?      ( $$-$$f )
    [ over ] dip  compare [ 0 ] [ tib ^strings'append 10 ^strings'appendChar -1 ] if ;
---reveal---
  : heredoc ( "-$ )
    heap [ remapping [ getDelimiter prepare [ readLine append? ] while nip ] preserve ] preserve ;
}}

heredoc [END]
1 2 3
  4 5 6
    7 8 9
[END]