make "roman.rules [
  [1000 M] [900 CM] [500 D] [400 CD]
  [ 100 C] [ 90 XC] [ 50 L] [ 40 XL]
  [  10 X] [  9 IX] [  5 V] [  4 IV]
  [   1 I]
]

to roman :n [:rules :roman.rules] [:acc "||]
  if empty? :rules [output :acc]
  if :n < first first :rules [output (roman :n bf :rules :acc)]
  output (roman :n - first first :rules  :rules  word :acc last first :rules)
end