\begin{tikzpicture}[node distance=1em]
\node (s1) {\verb#>>|.#};
\node (d1) [left=of s1.north,yshift=-3em] {\verb#delay 500#};
- \node (s2) [right=of s1.south,xshift=-3em,yshift=-3em,fill=gray!15,label={[xshift=1em,label distance=-5pt]above:{\tiny interpreter}}] {\verb#writeD D3 st >>=.# $\lambda x\shortrightarrow$};
+ \node (s2) [right=of s1.south,xshift=-3em,yshift=-3em,fill=gray!15,label={[xshift=1em,label distance=-5pt]above:{\tiny interpreter}}] {\verb#writeD D3 st >>=. \x->#};
\node (s3) [node distance=-.25em,below=of s2.south,fill=gray!15] {\verb#blink (Not x)#};
\draw (s1.south) -- (d1.north);
\draw (s1.south) -- ([xshift=-1em]s2.north);