Not _exactly_ what you want, but you can start from Regex::PreSuf.

You'd have to be able to enumerate the roman numerals you want to match to be able to use it directly, though...

$ perl -MRegex::PreSuf -e'my $re = presuf(qw(I II III IV V VI VII VIII
+ IX X));
print "$re\n";'
(?:I(?:II|[IVX])|VI(?:II|I)?|[IVX])
[download]

That could get pretty wild :)
--
Mike