Post processing of rendered content

is there a way to allow some html content to go thru the render step and remain as html rather than <&> 's being translated to <&> so i can post-process my own JSP-style tags ?  I'm aware asciidoctor does have an include feature but i've got a lot of legacy scripts i'd hate to change  :-P

so for example my payload would look like this:

== Heading One

Ok, kids - here is your class assignment for today:
<% include '/WEB-INF/includes/samplefragment.html' %>

giving something like :
<div id="content">
<div class="sect1">

Heading One

<div class="sectionbody">
<div class="paragraph">
<p>Ok, kids - here is your class assignment for today:
<br />Write an essay
</p>
</div>
</div>
</div>
</div>

yes using passthrough macro or triple plus sign:

http://asciidoctor.org/docs/user-manual/#passthrough-macros

ok, may have spotted this. if i put 3 plus signs around the text, it gets thru unscathed. so :

hi +++all you<br />+++ kids

gives me

hi all you<br /> kids

--- also saw a reference to using 4 plus signs but dunno if that's the same thing :-}