package Calc::Euro;
use strict;
use Carp;
my %rates = qw(
        LUF 40.3399     ATS 13.7603     BEF 40.3399
        NLG 2.20371     FIM 5.94573     FRF 6.55957
        DEM 1.95583     GRD 340.75      IEP 0.787564
        ITL 1936.27     PTE 200.482     ESP 166.386 
);

sub new {
    my ($proto, $currency) = @_;
    my $rate = defined $currency && (
                   $rates{uc $currency} || 0 + $currency
               ) ||
               ( ref $proto eq __PACKAGE__ ?
                   $$proto
               :
                   croak("Invalid currency")
               );
    return bless \$rate, ref($proto) || $proto;
}

sub to_euro {
    my ($self, $amount) = @_;
    return $amount / $$self;
}

sub to_national {
    my ($self, $amount) = @_;
    return $amount * $$self;
}

sub from_euro     { goto &to_national }
sub from_national { goto &to_euro }
sub clone         { goto &new }

##</code><code>##

#!/usr/bin/perl -w

use strict;
use Calc::Euro;

my $eurocalc = Calc::Euro->new('NLG');
print $eurocalc->to_national(1), "\n"; # 2.20371

my $anothercalc = $eurocalc->clone();
print $eurocalc->to_national(1), "\n"; # 2.20371

$eurocalc = Calc::Euro->new('BEF');
print $anothercalc->from_euro($eurocalc->to_euro(20)), "\n";
# approx 1

my $foo = Calc::Euro->new(1.5);
print $foo->to_national(2), "\n"; # 3

##</code><code>##

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$