You don't need to set a variable in that case:
if (($chr(33) isin $2) || ($chr(63) isin $2)) return
In fact, in that specific case, you don't even need to use the $chr identifier:
if ((! isin $2) || (? isin $2)) return
If you have a very long list of characters to check, you could use this method (this example would detect !?@%^& in $2):
if ($remove($2,!,?,@,%,^,&) != $2) return
In the above 2 examples, remember that the # character cannot be used because it is a shortcut to $chan. Use $chr(35) instead.