Possible Duplicate:
A Regex that will never be matched by anything
I have a script that takes a regex as a parameter. By default I want to set the regex to something that will never match any string, so I can simply say
if ($str =~ $regex)
without e.g. having to check defined($regex) first.
I came up with
qr/[^\s\S]/
but don't know if this will match some utf8 character that is neither a space nor a non-space.