2.5.1. Problem

2.5.2. Solution

use Roman;
$roman = roman($arabic);                        # convert to roman numerals
$arabic = arabic($roman) if isroman($roman);    # convert from roman numerals

2.5.3. Discussion

The module only deals with Roman numbers from 1 to 3999, inclusive. The Romans didn't represent negative numbers or zero, and 5000 (which 4000 is represented in terms of) uses a symbol outside the ASCII character set.

use Roman;
$roman_fifteen = roman(15);                         # "xv"
print "Roman for fifteen is $roman_fifteen\n";
$arabic_fifteen = arabic($roman_fifteen);
print "Converted back, $roman_fifteen is $arabic_fifteen\n";

Roman for fifteen is xv
Converted back, xv is 15

Or to print the current year:

use Time::localtime;
use Roman;
printf "The year is now %s\n", Roman(1900 + localtime->year);

The year is now MMIII

Now, if you happen to have Unicode fonts available, you'll find that code points U+2160 through U+2183 represent Roman numerals, including those beyond the typical ASCII values.

use charnames ":full";
print "2003 is \N{ROMAN NUMERAL ONE THOUSAND}" x 2, "\N{ROMAN NUMERAL THREE}\n";

2003 is

However, the Roman module doesn't yet have an option to use those characters.

Believe it or not, there's even a CPAN module that lets you use Roman numerals in arithmetic.

use Math::Roman qw(roman);
print $a  = roman('I'); #  I
print $a += 2000;       #  MMI
print $a -= "III";      #  MCMXCVIII
print $a -= "MCM";      #  XCVIII

2.5.4. See Also