sub check {
  $_ = "sendmail[[text to be captured from sendmail],relaying denied";

  (/sendmail\[.*?\[(.*?)\],.*?Relaying denied/i) and return ($1);
  (/gnu-pop3d\[.*?refused connect from (.*?)$/i) and return ($1);
  (/cucipop\[.*?authentication failure\s.*?\s(.*?)$/i) and return ($1);
  
  return "No match found";
};
print check,"\n";