I would use Exporter and create accessors for the data rather than accessing the data directly.

package Foo;

use warnings;
use strict;
use base 'Exporter';

our @EXPORT_OK = qw(
   some_data
   some_more_data
   fribble
);

sub some_data { 'foo' }
sub some_more_data { 'bar' }

my %gnarfles = (
    this => 1,
    that => 'one'
);

sub fribble {
    my $key = shift;
    if (exists $gnarfles{$key}) {
        return $gnarfles{$key};
    }
    else {
        die "No such value ($key)";
    }
}    

1;
[download]

And in your actual program:

use Foo qw'fribble some_data';

my $result = fribble($key);
[download]

By properly encapsulating your data in accessors, you make it much easier to extend and make it easier to validate. Also, by adding it to @EXPORT_OK instead of @EXPORT, you ensure that people only import the functions that they need and, more importantly, it is very easy to track down where the function came from.