We'll make sure that the element at that position is defined, true, and not the empty string:

  for my $i ( 0 .. $#to_clean )
  {
     next if defined $to_clean[ $i ] and $to_clean[ $i ];
     next unless $to_clean[ $i ] eq '';
  }
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If testing for a truth value as above, why is there a need to separately test for an empty string? As empty string will evaluate to a false value, 2d "next" statement is of no use.