Case $x$;$y$ =$>$ ${\it body}$($x$;$y$) ${\it cont}$($x_{1}$,$z$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$Case $x_{1}$ of inl($\_$) $\Rightarrow$ ${\it cont}$($z$,$z$) ; inr($x_{2}$) $\Rightarrow$ $x_{2}$/$x_{3}$,${\it x2@}_{0}$. ${\it body}$($x_{3}$;${\it x2@}_{0}$)