gt; -&gt; &lt;program&gt; [| &lt;match-branches&gt;]</span></i>
<i><span style='color:#898887;'>   &lt;placeholder&gt; ::= %&lt;ident&gt;</span></i>

<i><span style='color:#898887;'>   &lt;directive&gt; is one of the interpreter directives for defining new operators or</span></i>
<i><span style='color:#898887;'>   importing definitions from modules</span></i>

<i><span style='color:#898887;'>   &lt;empty&gt; signifies lack of tokens. It denotes a `nil' value -- the same as `()'.</span></i>
<i><span style='c