I work with Perl. And that language has some rather queer exceptions. One example: @my_array is … you guessed, an array! $#my array is the highest index currently occupied. But EmEditor considers everything beyond the ‘#’ as comment. And there are many more exceptions.
Perl is not a very good example. It is mathematically proven that it cannot be statically parsed (that is, without running the script itself), not to mention doing this with only regexps, having no customizable lexer and parser.
Of course, it does not mean that there is no place for improvements — some common and non-contradictory expressions still can be detected and highlighted, but with Perl’s versatility it’s quite a troublesome task. As a Perl developer, I would be extremely glad to see improvements in this area too…