def do_execute(self):
        """
        The actual execution of the actor.

        :return: None if successful, otherwise error message
        :rtype: str
        """
        fname = str(self.input.payload)
        spattern = str(self.resolve_option("regexp"))
        pattern = None
        if (spattern is not None) and (spattern != ".*"):
            pattern = re.compile(spattern)
        if (pattern is None) or (pattern.match(fname)):
            os.remove(fname)
        self._output.append(self.input)
        return None