Suppose I have a regex language supporting literals, positive and negative character classes, ordered alternation, and the greedy quantifiers ?, *, and +. (This is essentially a subset of PCRE without backreferences, look-around assertions, or some of the other fancier bits.) Does adding the nongreedy quantifiers ??, *?, and +? increase the expressive power of this formalism?
Put another way, given a pattern S containing a nongreedy quantifier, can that pattern be rewritten to an equivalent pattern T which contains no nongreedy quantifiers?
If this question has been considered in the literature, I'd appreciate any references which anyone can provide. I was able to turn up almost no theoretical work on the expressive power of extended regex formalisms (beyond the usual things about how backreferences move you from regular languages to context-free grammars).