my $default_theme = get_default_theme();
my $global_config = read_config('/path/to/config_file');
my $theme_config = read_config($global_config->{theme_file});
my $current_mode = get_current_mode();

my $theme = defined $global_config->{modes}{$current_mode}{theme} ?
                    $global_config->{modes}{$current_mode}{theme} :

            defined $theme_config->{current_theme}                ?
                    $theme_config->{current_theme}                :

            defined $default_theme                                ?
                    $default_theme                                :

                    'none';