If you need to store more information, consider a more complex data structure. reptile suggests a hash of lists. I would choose a hash of hashes.

my %data = (
    'US' => {
        Florida => 'Miami',
        Illinois => 'Chicago',
        New York => 'New York City' },
    'Canada' => {
        British Columbia => 'Alberta',
        Saskatchewan => 'Saskatoon',
        Ontario => 'Toronto' }
);
[download]

The appropriate perldoc pages are perldsc and perlref.

(Oh, a hash is an associative array. That means that it takes the first element -- New York, for example -- and runs it through a hashing algorithm to generate a unique index, which helps it locate the key -- New York City -- in an internal data structure. If the hashing algorithm is good, "New York" will always come up with the same hash value, which is why duplicate keys are not very useful.)