Normally $all would have been a template too, but if it wasn't going to contain HTML I guess its not strictly needed. However its addvisable not to hard code stuff into files and to use the template/phrase system where posible.
Not sure if your evals will work like that, here's how they are done throughout vB3:
PHP Code:
eval('$threadmanagement = "' . fetch_template('newpost_threadmanage') . '";');