This worked for me:
(&&)|(\|\|)|(--)|(__)|(/\*)
Bear in mind that that Regex will find those strings - so if you get a match you need to reverse the decision!
To get a match when none of the sequences are there, you'd need to use a negative lookahead:
^(?!.*(&&)|(\|\|)|(--)|(__)|(/\*)).*$
Which ./.. looks pretty impenetrable!