There's a HUGE difference between PCRE and other, older forms of regular expressions (basic, extended, posix), with the latter having significant limitations. I chose to use PCRE in my request here, because it is the correct choice should integrating a regular expression language become a possibility. Let's not muddy the waters yet with implementation details.
Regular expressions can be trivial or quit complex, depending upon the situation and needs. But it would be a mistake to caution or worry that "it has a very limited scope". They are a powerful *generalized* solution that obsolete many of today's MC functions (RemoveRight/Left, Left, Mid, etc). These are the "very limited scope" solutions. Unless you understand finite automata and language theory, its best not to comment on RE's strengths and weaknesses. They solve an extraordinary number of problems, with simplicity and generality, that users here face routinely.
Marko - with today's expressions, for example, how would one remove all characters up to the first space in a text? Or strip an arbitrary number of certain pronouns or determiners or a sequence of known or arbitrary number of characters? Regular expressions make this kind of stuff trivial and easier to read. Many of today's expressions shared by users are obscenely long and and needlessly complex.
Or lowercase all prepositions not handled already by MC? This is it (just a few prepositions below):
s/\b(up|on|in|under|through)\b/\1/
Anyway, I hope folks see the power of these and show their interest.
More info:
http://en.wikipedia.org/wiki/Regular_expression