diff --git a/xCAT-server/lib/xcat/plugins/ipmi.pm b/xCAT-server/lib/xcat/plugins/ipmi.pm
index 3e5650939..9718d668a 100644
--- a/xCAT-server/lib/xcat/plugins/ipmi.pm
+++ b/xCAT-server/lib/xcat/plugins/ipmi.pm
@@ -3,8 +3,9 @@
 #modified by jbjohnso@us.ibm.com
 #(C)IBM Corp
 
-$xcat_plugins{ipmi}="this";
 package xCAT_plugin::ipmi;
+use strict;
+use warnings "all";
 
 use Storable qw(store_fd retrieve_fd thaw freeze);
 use xCAT::Utils;
@@ -14,8 +15,8 @@ my $tfactor = 0;
 my %bmc_comm_pids;
 
 require Exporter;
-@ISA = qw(Exporter);
-@EXPORT = qw(
+our @ISA = qw(Exporter);
+our @EXPORT = qw(
 	ipmiinit
 	ipmicmd
 );
@@ -33,7 +34,6 @@ sub handled_commands {
 }
 
     
-use strict;
 use Data::Dumper;
 use POSIX "WNOHANG";
 use IO::Handle;
diff --git a/xCAT-server/lib/xcat/plugins/mknb.pm b/xCAT-server/lib/xcat/plugins/mknb.pm
index 913c96c10..05f63d16d 100644
--- a/xCAT-server/lib/xcat/plugins/mknb.pm
+++ b/xCAT-server/lib/xcat/plugins/mknb.pm
@@ -1,4 +1,5 @@
 package xCAT_plugin::mknb;
+use strict;
 use File::Temp qw(tempdir);
 use xCAT::Utils;
 use File::Path;
diff --git a/xCAT-server/lib/xcat/plugins/nodestat.pm b/xCAT-server/lib/xcat/plugins/nodestat.pm
index 85c014eec..e3c2f05cb 100644
--- a/xCAT-server/lib/xcat/plugins/nodestat.pm
+++ b/xCAT-server/lib/xcat/plugins/nodestat.pm
@@ -1,4 +1,6 @@
 package xCAT_plugin::nodestat;
+use strict;
+use warnings;
 
 use Socket;
 use IO::Handle;
@@ -78,7 +80,7 @@ sub preprocess_request
 
     # find service nodes for requested nodes
     # build an individual request for each service node
-    $sn = xCAT::Utils->get_ServiceNode($nodes, $service, "MN");
+    my $sn = xCAT::Utils->get_ServiceNode($nodes, $service, "MN");
 
     # build each request for each service node
     my @requests;