Roman numerals? I have never encountered a regex implementation where '\d' matches 'X'. It's certainly not the case for Javascript: http://regexpal.com/?flags=g®ex=\d%2B&input=10%0Ax%0AX%0A...
http://www.charbase.com/2169-unicode-roman-numeral-ten
(even more in http://www.charbase.com/block/number-forms)
I'm not sure if Javascript matches these in its \d pattern, however, but I think that most regexp engines default to the ascii [0-9] unless you are using \p{Number}.
false