Here's a simple function for Roman numerals:

use strict;
use warnings;

for (1..100) {
    print roman($_), "\n";
}

BEGIN {
    my %roman = ( 1 => 'I', 4 => 'IV', 5 => 'V', 9 => 'IX', 10 => 'X',
        40 => 'XL', 50 => 'L', 90 => 'XC', 100 => 'C', 400 => 'CD',
        500 => 'D', 900 => 'CM', 1000 => 'M' );
    my @roman = sort { $b <=> $a } keys %roman;

    sub roman {
        my ($n, $r) = $_[0];
        for (@roman) {
            next if $_ > $n;
            $r .= $roman{$_} x ($n / $_);
            $n = $n % $_;
        }
        return $r;
    }
}
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I discovered a relatively simple explanation for the algorithm here.