If you were to store this in a relational database, you could just dump it in a table and build three indices on top of it. Well, we can do something similar in Perl (except that our indices are not at all suitable for range queries), using hashes for the indices.

Here's some example code (assuming the codes and countries are unique, but currencies aren't).

#!/usr/bin/perl -w

use strict;
use warnings 'all';

my (%code, %country, %currency);

while (<DATA>) {
    my $info = [split];
    $code            {$info -> [0]}  =  $info;
    $country         {$info -> [1]}  =  $info;
    push @{$currency {$info -> [2]}} => $info;
}

sub info_by_code {
    my $code = shift;
    $code {$code}
}  

sub info_by_country {
    my $country = shift;
    $country {$country}
}
 
sub info_by_currency {
    my $currency = shift;
    @{$currency {$currency}}
}
 
print "Code for Germany is ", info_by_country ("GER") -> [0], "\n";
print "People pay in Euros in ",
       join (", " => map {$_ -> [1]} info_by_currency ("EUR")), "\n";
 
__END__
US USA USD 
CA CAN CND
DE GER EUR
IT ITA EUR
FR FRA EUR
NL NET EUR
BE BEL EUR
CH SWI SFR
    
    
$ ./countries
Code for Germany is DE
People pay in Euros in GER, ITA, FRA, NET, BEL
$
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Abigail