Allows conversion between Roman and Arabic algarisms

 Text::Roman supports both conventional Roman algarisms (which range
 from 1 to 3999) and Milhar Romans, a variation which uses a bar
 across the algarism to indicate multiplication by 1_000. For the
 purposes of this module, acceptable syntax consists of an underscore
 suffixed to the algarism e.g. IV_V = 4_005. The term Milhar
 apparently derives from the Portuguese word for "thousands" and the
 range of this notation extends the range of Roman numbers to 3999 *
 1000 + 3999 = 4_002_999.