my @thresh;
  my $total = 0;
  for ( keys %hash )
  {
    $total += $hash{$_};
    push @thresh, [ $total, $_ ];
  }

  my $string;
  for ( 1 .. 30 )
  {
    my $r = rand $total;
    my $i = 0;
    while ( $r > $thresh[$i][0] ) { $i++; }
    $string .= $thresh[$i][1];
  }