namelist2config: changed duplicate key feedback to show old value

namelist2config

@@ -168,7 +168,11 @@ while(<>) {
             $open_value = 1;
             $direct and print("      $key = ");
             if(exists $namelist_group->{$key}) {
-                warn("Hey: duplicate key '$key'");
+                my $value = join(', ', @{$namelist_group->{$key}});
+                my $line = ' '.$_;
+                $line =~ s/\s+/ /g;
+                warn("Hey: duplicate key, current value '$value'\n");
+                warn("$.:$line\n"); 
                 $key = '#DUPLICATE# '.$key;
             }
             $namelist_group->{$key} = [];