make "patterns [[?] [? ?] [? ? ?] [? ?2] [?2] [?2 ?] [?2 ? ?] [?2 ? ? ?] [? ?3]]

to digit :d :numerals
  if :d = 0 [output "||]
  output apply (sentence "\( "word (item :d :patterns) "\)) :numerals
end
to digits :n :numerals
  output word ifelse :n < 10 ["||] [digits int :n/10 bf bf :numerals] ~
              digit modulo :n 10 :numerals
end
to roman :n
  if or :n < 0 :n >= 4000 [output [EX MODVS!]]
  output digits :n [I V X L C D M]
end

print roman 1999  ; MCMXCIX
print roman 25    ; XXV
print roman 944   ; CMXLIV