Template Preprocessing and BEM CSS syntax problem

expression03.thtest

%EXTENDS ../html5.01.common
# ------------------------------------------------------------
%CONTEXT
size = 123
# ------------------------------------------------------------
%INPUT
<p th:text="`00${size}00`">...</p>
<p th:text="`00__${size}__00`">...</p>
<p th:text="'00__${size}__00'">...</p>
<p th:text="'00__${size}00'">...</p>
<p th:text="'00'something'00'">...</p>
<p th:text="'00something00'">...</p>
# ------------------------------------------------------------
%OUTPUT
<p>0012300</p>
<p>00__123__00</p>
<p>00__${size}__00</p>
<p>00__${size}00</p>
<p>00something00</p>
<p>00something00</p>