[ 32|   {get value of Roman digit on stack}
  $'m= $[\% 1000\]? ~[
  $'d= $[\% 500\]? ~[
  $'c= $[\% 100\]? ~[
  $'l= $[\% 50\]? ~[
  $'x= $[\% 10\]? ~[
  $'v= $[\% 5\]? ~[
  $'i= $[\% 1\]? ~[
  % 0
  ]?]?]?]?]?]?]?
]r:

0           {accumulator}
^r;!        {read first Roman digit}
[^r;!$][    {read another, and as long as it is valid...}
  \$@@\$@@  {copy previous and current}
  \>[\_\]?  {if previous smaller than current, negate previous}
  @@+\      {add previous to accumulator}
]#
%+.         {add final digit to accumulator and output}
10,         {and a newline}