my @words = get_words_to_check();

my %hash = map { $_ => 1 } @words;

while (my $line = <>)
{
  chomp $line; 
  delete $hash{$line} if exists $hash{$line}; # The if exists isn't required here, but it does make it look cleaner
}

my @good_words = grep { exists $hash{$_} } @words; # Keep the original order
my @good_words_2 = keys %hash; # Don't care about the original order


##</code><code>##

my $index = 0;
LINE: while (my $line = <>)
{
  chomp $line;
  
  # While the word in the dictionary is past (or equal) to the word to check
  while ($line ge $words[$index])
  {
    # Store the word as OK, unless it is equal to the current dict word
    push @good_words, $words[$index] unless $line eq $words[$index];

    # Use the next word from the list of words to check, if any
    last LINE if ++$index == @words;
  }
}