Index: head/en_US.ISO8859-1/books/porters-handbook/uses/chapter.xml
===================================================================
--- head/en_US.ISO8859-1/books/porters-handbook/uses/chapter.xml
+++ head/en_US.ISO8859-1/books/porters-handbook/uses/chapter.xml
@@ -1167,16 +1167,51 @@
       <application>Perl</application>, <application>PHP</application>,
       <application>Python</application>,
       <application>Ruby</application>, <application>Tcl</application>,
-      and <application>Tk</application> are supported by default.  To
-      support another interpreter, set
-      <varname>SHEBANG_LANG</varname>,
-      <varname><replaceable>interp</replaceable>_OLD_CMD</varname> and
-      <varname><replaceable>interp</replaceable>_CMD</varname>.  For
-      example:</para>
+      and <application>Tk</application> are supported by
+      default.</para>
+
+    <para>There are three configuration variables:</para>
+
+    <variablelist>
+      <varlistentry>
+	<term><varname>SHEBANG_LANG</varname></term>
+
+	<listitem>
+	  <para>The list of supported interpreters.</para>
+	</listitem>
+      </varlistentry>
+
+      <varlistentry>
+	<term><varname><replaceable>interp</replaceable>_CMD</varname></term>
+
+	<listitem>
+	  <para>The path to the command interpreter on &os;.  The
+	    default value is
+	    <literal>${LOCALBASE}/bin/<replaceable>interp</replaceable></literal>.</para>
+	</listitem>
+      </varlistentry>
+
+      <varlistentry>
+	<term><varname><replaceable>interp</replaceable>_OLD_CMD</varname></term>
+	<listitem>
+	  <para>The list of wrong invocations of interpreters.  These
+	    are typically obsolete paths, or paths used on other
+	    operating systems that are incorrect on &os;.  They
+	    will be replaced by the correct path in
+	    <varname><replaceable>interp</replaceable>_CMD</varname>.
+	    This list will always be part of
+	    <varname><replaceable>interp</replaceable>_OLD_CMD</varname>:
+	    <literal>"/usr/bin/env <replaceable>interp</replaceable>"
+	      /bin/<replaceable>interp</replaceable>
+	      /usr/bin/<replaceable>interp</replaceable></literal>.</para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+
+    <para>To add another interpreter, set
+      <varname>SHEBANG_LANG</varname>.  For example:</para>
 
-    <programlisting>SHEBANG_LANG=	lua
-lua_OLD_CMD=	/usr/bin/lua
-lua_CMD=	${LOCALBASE}/bin/lua</programlisting>
+    <programlisting>SHEBANG_LANG=	lua</programlisting>
 
     <para><literal><replaceable>interp</replaceable>_OLD_CMD</literal>
       will contain multiple values.  Any entry with spaces must be