title: extract only words that do not contain words ending with a particular letter combination (using regex only)
body: <p>I have this list of Portuguese language words <a href="https://raw.githubusercontent.com/pythonprobr/palavras/master/palavras.txt" rel="nofollow noreferrer">https://raw.githubusercontent.com/pythonprobr/palavras/master/palavras.txt</a>. I want to extract only words that do not end in "er" or "ar". I have been trying to apply the methods in the answers to this question <a href="https://stackoverflow.com/questions/22964598/regex-not-matching-words-ending-with-impl">Regex not matching words ending with &quot;Impl&quot;</a> but I can't make it work.
  I've been using the command like this from this answer <a href="https://stackoverflow.com/a/22964675/10824251">https://stackoverflow.com/a/22964675/10824251</a> : <code>$ grep -oP '[A-Z][A-Za-z\d]*(\?&lt;! er) [ [A-Z] [A-Za-z \\ d] * (\? &lt;! er)] ' palavra.txt &gt; output.txt</code></p>