The classic way to do this is to export those variables via Exporter.
Another, easier (tidier) way is to do so using Exporter::Tidy. That way, you get to export the lexical so that in your module you don't have the overhead that package global variables normally have.
package Foo;
use Exporter::Tidy _map => { '$foo' => \my $foo };
$foo = 3;
And then, in the code that uses the package, unchanged:
use Foo qw($foo);
print $foo;
Juerd
# { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }