The last task, to match a question, can be solved quite easily by reversing the string.
in reply to Death to Dot Star!
Note that it's OK to use .*? here. And due to optimizations in the regex engine it's even faster to use it than a negative char class, if the following pattern is constant as it is in this case.
my ($m) = reverse($myvar) =~ /"\?(.*?)"/s;
$m = reverse $m;
print "matched <$m>\n";
It's also very easy to make it work for escaped quotes by adding a negative look-ahead.
my ($m) = reverse($myvar) =~ /"\?(.*?)"(?!\\)/s;
Note that here you must use .*? instead of a negative char class since you want the engine to backtrack.