<p>I can never remember the differences in regular expression syntax used by tools like <a href="http://en.wikipedia.org/wiki/Grep" rel="noreferrer">grep</a> and <a href="http://en.wikipedia.org/wiki/AWK" rel="noreferrer">AWK</a>, or languages like Python and PHP. Generally, Perl has the most expansive syntax, but I'm often hamstrung by the limitations of even <code>egrep</code> ("extended" <code>grep</code>).</p>

<p>Is there a site that lists the differences in a concise and easy-to-read fashion?</p>

[{'answer_id': 23223, 'author': 'Konrad Rudolph', 'author_id': 1968, 'author_profile': 'https://Stackoverflow.com/users/1968', 'pm_score': 3, 'selected': False, 'text': '<p>I find this site helpful: <a href="http://www.regular-expressions.info/" rel="noreferrer">http://www.regular-expressions.info/</a></p>\n\n<p>Other than that, I use the corresponding documentation extensively and I believe, all said and done, there\'s no way around that.</p>\n'}, {'answer_id': 23229, 'author': 'Kibbee', 'author_id': 1862, 'author_profile': 'https://Stackoverflow.com/users/1862', 'pm_score': 4, 'selected': True, 'text': '<p><a href="https://rads.stackoverflow.com/amzn/click/com/0596528124" rel="nofollow noreferrer" rel="nofollow noreferrer">Mastering Regular Expressions</a>, devotes the last four chapters to Java, PHP, Perl, and <a href="http://en.wikipedia.org/wiki/.NET_Framework" rel="nofollow noreferrer">.NET</a>.  One chapter for each. From what I know, the <a href="https://rads.stackoverflow.com/amzn/click/com/0596514271" rel="nofollow noreferrer" rel="nofollow noreferrer">pocket edition</a> contains just those final four chapters.  </p>\n'}, {'answer_id': 23232, 'author': 'yukondude', 'author_id': 726, 'author_profile': 'https://Stackoverflow.com/users/726', 'pm_score': 4, 'selected': False, 'text': '<p>For my own future reference, I\'ll offer the <a href="http://www.greenend.org.uk/rjk/2002/06/regexp.html" rel="noreferrer">Regexp Syntax Summary</a> page which contrasts the syntax for <code>grep</code>, <code>egrep</code>, Emacs, Perl, Python, and Tcl. As expected, Perl supports the greatest variety of operators, but Python looks equally capable, if not more so.</p>\n'}]
['https://Stackoverflow.com/questions/23216', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/726/']