Thanks I found the solution on the link you provided.

# Assumes only 1 currently opened window with target _blank
sub select_target_blank_window {
    my ($self, $timeout) = @_;
    my $window_name;
    for (1 .. $timeout / 100) {
       ($window_name) = grep {/selenium_blank\d+/} $self->get_all_wind
+ow_names;
       last if defined $window_name;
       $self->pause(100);
    }
    croak "Timed out waiting to select blank target window" if ! defin
+ed $window_name;
    return $self->select_window($window_name);
}
[download]

Now to figure out how to get a value in a form. It is a drop down list consisting dates. sel->type("xxx",15"); does not work. nor does