use IPC::Open3 qw( open3 );

{
   local *FROM_MYSQLDUMP;
   open(local *INPUT,  '<', '/dev/null') or die $!;
   open(local *OUTPUT, '>', "$backup_dir/mydatabase.sql.gz") or die $!;

   my $mysqldump_pid = open3('<&INPUT', \*FROM_MYSQLDUMP, '>&STDERR',
      mysqldump => (
         '--add-drop-table',
         '-u'.'root',
         '-p'.'password',
         'mydatabase',
      ),
   );

   my $gzip_pid = eval {
      open3('<&FROM_MYSQLDUMP', '>&OUTPUT', '>&STDERR',
         gzip => ( '-9c' ),
      )
   };   

   if (!$gzip_pid) {
      my $e = $@;
      kill(KILL => $mysqldump_pid);
      waitpid($mysqldump_pid, 0);
      die($e);
   }
   
   waitpid($mysqldump_pid, 0);
   waitpid($gzip_pid, 0);
}