Need to find boardname variable while in post.php

[Patrick Egan]

I am trying to modify the reply subject for notification emails from the stock Topic reply: My topic subject to something like this  Re: [BOARDNAME] My topic subject 

The language variable looks like this now...

$txt['notification_reply_subject'] = 'Topic reply: %s';

And I've gotten this far but I can not figure out what the variable for the current board name is.

$txt['notification_reply_subject'] = 'Re: [' . $context['boardname'] . '] %s';

Can anyone tell me what variable to use here