: (parse-multiline-string) ( start-index end-text -- end-index )
lexer get line-text>> [
2dup start
- [ rot dupd >r >r swap subseq % r> r> length + ] [
+ [ rot dupd [ swap subseq % ] 2dip length + ] [
rot tail % "\n" % 0
lexer get next-line swap (parse-multiline-string)
] if*