How to list all files in the directories

1. 
   

   how to list all files in parent and sub directory for multilpe dir

   
   

   $dir="/home/httpd/cgi-bin/r/met";

   
   

   
   opendir(DIR,"/home/httpd/cgi-bin/r/met")||die"error";
   
   while($line=readdir DIR)
   {
   
   print"$line\n";
   
   opendir DIR1,"$dir/$line"||die"error";
   
       while($line1=readdir DIR1)
       {
        print"$line1\n";
        }
   }
   closedir DIR;
   closedir DIR1;