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foreach my $w (@words) {
  my $lw = length $w;
  if($cols_left > $lw) {
    $para .= ' ' if $cols_left < $self->columns;
    $para .= $w;
    $cols_left -= $lw;
  }
  else {
    $para .= "\n$w";
    $cols_left = $self->columns - $lw;
  }
}