Convert three variable assignments to the usage of combined operators

[elfring]

👀 Some source code analysis tools can help to find opportunities for improving software components.
💭 I propose to increase the usage of combined operators accordingly.

diff --git a/Sldb.pm b/Sldb.pm
index 32fa3d9..872bec1 100644
--- a/Sldb.pm
+++ b/Sldb.pm
@@ -1502,7 +1502,7 @@ sub getFirstRangeAddr {
 # Called by computeAllUserIps()
 sub getLastRangeAddr {
   my $ip=shift;
-  $ip=$ip-($ip%256)+255;
+  $ip -= ($ip%256) - 255;
   return $ip;
 }
 
diff --git a/slMonitor.pl b/slMonitor.pl
index 3186ec3..13e81ed 100755
--- a/slMonitor.pl
+++ b/slMonitor.pl
@@ -555,7 +555,7 @@ sub getFirstRangeAddr {
 
 sub getLastRangeAddr {
   my $ip=shift;
-  $ip=$ip-($ip%256)+255;
+  $ip -= ($ip%256) - 255;
   return $ip;
 }
 
diff --git a/sldbLi.pl b/sldbLi.pl
index d9a761e..613f5dc 100755
--- a/sldbLi.pl
+++ b/sldbLi.pl
@@ -450,7 +450,7 @@ sub formatArray {
       $title="[$title]";
       $title=(' ' x int(($rowLength-realLength($title))/2)).$title.(' ' x ceil(($rowLength-realLength($title))/2));
     }else{
-      $title=$title.':';
+      $title .= ':';
     }
     unshift(@rows,$title);
   }