sub asubroutine   {
      $my number=shift ;   # $number takes the value of 20
      if ( not defined ($array[$number]))	{	
           print "There is no such element $number in the array.\n";
           return;
      }
     my $x=$array[$number];
      if (defined $x->[1])  {
            if (@{$x->[3]}>0)	{
               # Do something
            }
       }
}