[Tabasco]

I think this only works in UF and newer clients, but the SendWebLink member of client is what you're looking for.

I do quite a bit with the in-game browser, but in its simplest form I have this wrapper in a plugin.

sub OpenURL
{
    my $url = shift;
    my $client = plugin::val('client');

    $client->SendWebLink($url);
}