perl6-slang-roman lets you write your Perl 6 code using Roman numerals:

use Slang::Roman



sub conjunctivus( Int $a, Int $b ) { $a + $b }

say conjunctivus( 0rIV, 0rVI );

# 10



And by the way, yes, it's fully Unicode compliant, so you can even write your numbers with \c[ROMAN NUMERAL ONE HUNDRED THOUSAND]. There's apparently a method of adding overbars to your Roman numerals that extends their range into the millions and beyond, but I think that I probably should leave well enough alone.