Example hook callback with contextual conditionals

gistfile1.aw

/**
 * Hook into hypothetical action hook
 */
function themeslug_after_post() {
     // Let's only do something on
     // single blog posts
     if ( is_single() ) {
          // output a hypothetical related posts function
          related_posts();
     }
}
// Hook our callback into the hypothetical 'after_post' hook
add_action( 'after_post', 'themeslug_after_post' );