\begin{tabbing}
(\=(((BoolCasesOnCExp 0 $\leq$z $x$) \+
\\[0ex]CollapseTHENM (AbReduce 0))$\cdot$) 
\\[0ex]CollapseTHEN (
\-\\[0ex](Auto\_aux (first\_nat 1:n) ((first\_nat 2:n),(first\_nat 3:n)) (first\_tok :t) inil\_term)))$\cdot$
\end{tabbing}