Can I use Perl regular expressions to match balanced text?

    No, or at least, not by the themselves.

    Regexps just aren't powerful enough.  Although Perl's patterns aren't
    strictly regular because they do backtracking (the \1 notation), you
    still can't do it.  You need to employ auxiliary logic.  A simple
    approach would involve keeping a bit of state around, something 
    vaguely like this (although we don't handle patterns on the same line):

        while(<>) {
            if (/pat1/) {
                if ($inpat++ > 0) { warn "already saw pat1" } 
                redo;
            } 
            if (/pat2/) {
                if (--$inpat < 0) { warn "never saw pat1" } 
                redo;
            } 
        }

    A rather more elaborate subroutine to pull out balanced and possibly
    nested single chars, like ` and ', { and }, or ( and ) can be found
    on convex.com in /pub/perl/scripts/pull_quotes.