{ use constant DEFAULT_STEP => 100; # a DOT is printed every DEFAULT_STEP call
  use constant LINE         => 50;  # nb of DOT per line      
  use constant BLOCK        => 10;  # a SPACE is printed after BLOCK DOTs
  use constant DOT          => '.'; # probably no need to change this
  use constant SPACE        => ' '; # probably no need to change this
  my( $i, $j);
  sub progress
    { my $step= shift || DEFAULT_STEP;
      $i++;
      if( $i == $step)
        { $i=0;
          print STDOUT DOT;
          $j++;
          unless( $j % BLOCK)
            { print STDOUT SPACE;
              if( $j == LINE)
                { $j=0;
                  print STDOUT "\n";
                }
            }
        }
    }
}