Is regular expression syntax regular? Regular expressions are equivalent to DFA's and describe regular languages, but is the language used to construct regular expressions regular?

My guess is that the original syntax (concat, | and *) is, but the Perl-style syntax is not (backtracking). As the newer syntax recognises non regular languages they must also generate non regular languages. If a DFA could recognise a non regular language then there would be a problem...
Both "original syntax" and PCRE's syntax is not regular. You need parenthesis to override operator precedence, which puts your syntax language into the territory of context free languages.