regex to match HTML tag

I would like to match an HTML <p ...> tag when the 1st char after closing tag > is in lower case, I saw some answers on this site to match p tag with attribute, but not a simple p tag (<p>), what change I need to do to match both?
Ex:

<p class="calibre1">All the while I was
<p>All the while I was
<p class="calibre1">all the while I was
<p>all the while I was

the regex should match the last 2 tags, the code that I have (/</?([^p](s.+?)?|..+?)>[a-z]/) matches only the 3rd, not the 4th tag