Creating a (global)-mapping

I figured it out myself.

function generate_the_excluded_array() {

  global $excluded_pages;
  $excluded_pages = array('Foo', 'Bar');
}
add_action( 'after_setup_theme', 'generate_the_excluded_array' );

And then it can be ‘imported’ using the global, as such:

function example_shortcode_definition() {

  global $excluded_pages;
  echo $excluded[0];
}
add_shortcode( 'example_shortcode', 'example_shortcode_definition' );