MT#12985 prevent ambiguity in rwr replace pattern

see http://perldoc.perl.org/perlre.html#Warning-on-\1-Instead-of-$1

Change-Id: I36dfa6cda570a4aef7da6ccc19e1d296c16f00c2

lib/NGCP/Panel/Utils/Subscriber.pm

@@ -1242,7 +1242,7 @@ sub apply_rewrite {
         $match = [ $match ] if(ref $match ne "ARRAY");
 
         $replace = shift @{ $replace } if(ref $replace eq "ARRAY");
-        $replace =~ s/\\(\d{1})/\$$1/g;
+        $replace =~ s/\\(\d{1})/\${$1}/g;
 
         $replace =~ s/\"/\\"/g;
         $replace = qq{"$replace"};