\[
\newcommand{\tr}{\Rightarrow}
\newcommand{\trs}{\tr^{\!\ast}}
\newcommand{\rlnm}[1]{\mathsf{(#1)}}
\newcommand{\rred}[1]{\xrightarrow{#1}}
\newcommand{\rreds}[1]{\mathrel{\xrightarrow{#1}\!\!^*}}
\newcommand{\cl}{\mathsf{Cl}}
\newcommand{\pow}{\mathcal{P}}
\newcommand{\matches}{\mathrel{\mathsf{matches}}}
\newcommand{\kw}[1]{\mathsf{#1}}
\newcommand{\andop}{\mathrel{\&\!\&}}
\newcommand{\orop}{\parallel}
\newcommand{\ff}{\mathsf{false}}
\newcommand{\tt}{\mathsf{true}}
\newcommand{\abra}[1]{\langle #1 \rangle}
\newcommand{\bnfnt}[1]{\abra{\small \textsf{#1}}}
\newcommand{\llbracket}{[\![}
\newcommand{\rrbracket}{]\!]}
\newcommand{\first}{\mathsf{First}}
\newcommand{\nullable}{\mathsf{Nullable}}
\newcommand{\follow}{\mathsf{Follow}}
\newcommand{\tm}[1]{\mathsf{#1}}
\newcommand{\nt}[1]{\mathit{#1}}
\newcommand{\Coloneqq}{::=}
\newcommand{\abs}[1]{|#1|}
\]
\[\begin{array}{rcl}
\nt{Cmd} &\Coloneqq& \tm{\$}\\[2mm]
&\mid& \nt{Exp}\ \tm{\$}\\[2mm]
&\mid& \tm{def}\ \tm{ident}\ \tm{(}\ \nt{ExpList}\ \tm{)}\ \tm{=}\ \nt{Exp}\ \tm{\$}\\[4mm]
\nt{Exp} &\Coloneqq& \tm{var} \\[2mm]
&\mid& \tm{ident}\ \tm{(}\ \nt{ExpList}\ \tm{)}\\[4mm]
\nt{ExpList} &\Coloneqq& \epsilon\\[2mm]
&\mid& \nt{Exp}\ \nt{ExpList'}\\[4mm]
\nt{ExpList'} &\Coloneqq& \epsilon\\[2mm]
&\mid& \tm{,}\ \nt{Exp}\ \nt{ExpList'}\\[4mm]
\end{array}\]