Function tostring from tutorial is missing

[nixxon]

In tutorial http://www.arclanguage.org/tut.txt, there is a function tostring that is like do except any output generated during the evaluation of its body is sent to a string, which is returned as the value of the whole expression. For example, the expression

(tostring                  
       (prn "domesday")
       (prn "book"))

should evaluate to string "domesday\nbook\n"