\begin{tabbing}
decrypt(${\it tab}$;${\it kval}$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=let $k$,$x$ = ${\it kval}$\+
\\[0ex]in
\\[0ex]if isl(st{-}lookup(${\it tab}$;$x$))
\\[0ex]then \=let ${\it key}$,${\it data}$ = outl(st{-}lookup(${\it tab}$;$x$))\+
\\[0ex]in
\\[0ex]if st{-}key{-}match(${\it tab}$;${\it key}$;$k$) then inl ${\it data}$  else inr $\cdot$  fi 
\-\\[0ex]else inr $\cdot$ 
\\[0ex]fi 
\-
\end{tabbing}