PerchSession, Adding additional values

In my APP I would like to ADD a couple key/value to PerchSession.

Where is the best place to do this? (php script)

My guess is perch/addons/apps/my_app/index.php but I am wondering if there is already another way to do this?

[index.php]

<?php
    # include the API
    include('../../../core/inc/api.php');

    $API  = new PerchAPI(1.0, 'my_app');

    # include your class files
    include('MyApp_Parents.class.php');
    include('MyApp_Parent.class.php');

    # Grab an instance of the Lang class for translations
    $Lang = $API->get('Lang');

    # Do what you want to do before output is started
    PerchSession::set('KEY','VALUE'); // <==================== Is there a better way/place for this?
    include('modes/parent.list.pre.php');

    # Top layout
    include(PERCH_CORE . '/inc/top.php');


    # Display your page
    include('modes/parent.list.post.php');


    # Bottom layout
    include(PERCH_CORE . '/inc/btm.php');
?>