runs these steps. They return a boolean.

<ol>

<li><p>Assert: <var>input</var> is not the empty string.

<li><p>Let <var>parts</var> be the result of <a>strictly splitting</a> <var>input</var> on

U+002E (.).

<li>

<p>If the last <a for=list>item</a> in <var>parts</var> is the empty string, then:

<ol>

<li><p>If <var>parts</var>'s <a for=list>size</a> is 1, then return false.

<li><p><a for=list>Remove</a> the last <a for=list>item</a> from <var>parts</var>.

</ol>

<li><p>If the last <a for=list>item</a> in <var>parts</var> is the empty string, then

<a for=list>remove</a> the last <a for=list>item</a> from <var>parts</var>.

<li><p>Let <var>last</var> be the last <a for=list>item</a> in <var>parts</var>.

<li>

<p>If <var>last</var> is non-empty and contains only <a>ASCII digits</a>, then return true.

<p>If <var>last</var> is not the empty string and contains only <a>ASCII digits</a>, then return

true.

<p class=note>The erroneous input "<code>09</code>" will be caught by the <a>IPv4 parser</a> at a

later stage.