#!/usr/bin/perl

use warnings;
use strict;

my $bar = "\x04\x4d";
my $foo = "044d";
my $string;

while ($foo =~ m/(..)/g) {
        $string .= chr($1);
}

print "string: $string\n";
print "bar: $bar\n";

Argument "4d" isn't numeric in chr at roman.pl line 11.
string: 
bar: M