[ $ ""
    swap 1000 /mod $ "M" rot of rot swap join swap
    dup   900 < not if [ 900 - dip [ $ "CM" join ] ]
    dup   500 < not if [ 500 - dip [ $  "D" join ] ]
    dup   400 < not if [ 400 - dip [ $ "CD" join ] ]
          100 /mod $ "C" rot of rot swap join swap
    dup    90 < not if [  90 - dip [ $ "XC" join ] ]
    dup    50 < not if [  50 - dip [ $  "L" join ] ]
    dup    40 < not if [  40 - dip [ $ "XL" join ] ]
           10 /mod $ "X" rot of rot swap join swap
    dup     9 < not if [   9 - dip [ $ "IX" join ] ]
    dup     5 < not if [   5 - dip [ $  "V" join ] ]
    dup     4 < not if [   4 - dip [ $ "IV" join ] ]
    $ "I" swap of join ]
                              is ->roman ( n --> $ )

  1990 dup echo say " = " ->roman echo$ cr
  2008 dup echo say " = " ->roman echo$ cr
  1666 dup echo say " = " ->roman echo$ cr