sub la{
    my $n = shift; 
    print ' ' x ( $n - $_ ), '*' x $_ 
        for 1 .. $n, reverse 0 .. $n - 1;
};;

la(3);;
   *
  **
 ***
  **
   *

la(6);;
      *
     **
    ***
   ****
  *****
 ******
  *****
   ****
    ***
     **
      *