The most common dialect is PCRE. Most languages have an implementation of either that or a superset of it. PCRE isn't exactly simple to begin with. That langua

The most common dialect is PCRE. Most languages have an implementation of either that or a superset of it. PCRE isn't exactly simple to begin with. That languages may implement it, or a superset of it, is exactly the problem. I know regular expressions very well, or rather I know regular languages and can fairly easily identify if a problem is solvable as a regular expressions. But once you start to go beyond that, it's not simple anymore and the benefit of a regular expression is lost.