diff --git a/src/warden-server/bin/registerReceiver.pl b/src/warden-server/bin/registerReceiver.pl
index cfa93b0be98fde6fc5cc0e26fbbd658f1a45fe41..3da44c19590e6276b1736dece9284a01556ee082 100755
--- a/src/warden-server/bin/registerReceiver.pl
+++ b/src/warden-server/bin/registerReceiver.pl
@@ -114,26 +114,26 @@ if ($script_version) {
 
 # check parameters definition
 switch () {
-  case {!defined $hostname} 		{WardenCommon::errMsg("Parameter '-n <hostname>' is not defined!")}
-  case {!defined $requestor} 		{WardenCommon::errMsg("Parameter '-r <requestor>' is not defined!")}
-  case {!defined $type}			{WardenCommon::errMsg("Parameter '-t <type>' is not defined!")}
-  case {!defined $ip_net_client} 	{WardenCommon::errMsg("Parameter '-c <cidr>' is not defined!")}
+  case {!defined $hostname} 		{WardenCommon::errMsg("Parameter '-n <hostname>' is not defined")}
+  case {!defined $requestor} 		{WardenCommon::errMsg("Parameter '-r <requestor>' is not defined")}
+  case {!defined $type}			{WardenCommon::errMsg("Parameter '-t <type>' is not defined")}
+  case {!defined $ip_net_client} 	{WardenCommon::errMsg("Parameter '-c <cidr>' is not defined")}
 }
 
 # check if type of event is allowed in validation hash
 my @valid_types = $WardenCommon::VALID_STRINGS{"type"};
-if (!($type ~~ @valid_types)) {
-  WardenCommon::errMsg("Unsupported type of events: '$type'!");
+unless ($type ~~ @valid_types) {
+  WardenCommon::errMsg("Unsupported type of events: '$type'");
 }
 
 # check validity of IP address (CIDR format)
 if ($ip_net_client !~ /^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\/(\d|[1-2]\d|3[0-2]))$/) {
-  WardenCommon::errMsg("Incorrect CIDR format of IP address: '$ip_net_client'!");
+  WardenCommon::errMsg("Incorrect CIDR format of IP address: '$ip_net_client'");
 }
 
 # check client ID
 if (defined $client_id && $client_id !~ /^\d+\z/) {
-  WardenCommon::errMsg("Parameter '-i <client_id>' is not a integer!");
+  WardenCommon::errMsg("Parameter '-i <client_id>' is not a integer");
 }
 
 # defined variables by script
@@ -159,11 +159,11 @@ if (defined $client_id) {
 }
 ($client_id_db, $hostname_db, $registered_db, $requestor_db, $client_type_db, $type_db, $receive_own_events_db, $ip_net_client_db, $valid_db) = $sth->fetchrow();
 # register receiver without user specified client_id
-if (!defined $client_id_db) {
+unless (defined $client_id_db) {
   $sth = $dbh->prepare("INSERT INTO clients VALUES (?,?,?,?,?,?,?,?,?,?,?);") or die "Cannot prepare statement: " . $dbh->errstr;
   my $ret_val = $sth->execute($client_id, $hostname, $registered, $requestor, $service, $client_type, $type, $receive_own_events, $description_tags, $ip_net_client, $valid) or die "Cannot execute statement: " . $sth->errstr;
   if ($ret_val == 1) {
-    if (!defined $client_id) {
+    unless (defined $client_id) {
       $client_id = $dbh->last_insert_id(undef, undef, "clients", undef);
     }
     sendMsg("info", "New receiver [ID: '$client_id', Hostname: '$hostname', Requestor: '$requestor', Type: '$type', ROE: '$receive_own_events', CIDR: '$ip_net_client'] was registered");