# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(?(DEFINE)(?<skip><ol>.*?<\\/ol>))(?&skip)(*SKIP)(*FAIL)|\s*<li\s+class="myclass">(.*?)<\\/li>\s*/<div class="newClass">$3<\/div>\n/gs;t' <<< "<ul>
<li class=\"myclass\">blablabla 1</li>
<li class=\"myclass\">blablabla 2</li>
<li class=\"myclass\">blablabla 3</li>
</ul>
<ol>
<li class=\"myclass\">blablabla 1</li>
<li class=\"myclass\">blablabla 2</li>
<li class=\"myclass\">blablabla 3</li>
</ol>
<ul>
<li class=\"myclass\">blablabla 1</li>
<li class=\"myclass\">blablabla 2</li>
<li class=\"myclass\">blablabla 3</li>
</ul>"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html