$word = qr/
   [[:alpha:]]      # Start with a letter.
   (?:
      [:^space:]*   # Hyphens, apostrophes, etc
      [[:alpha:]]   # Don't end on a punctuation mark.
   )?               # Catch single letter words.
/x;

##</code><code>##

$word = qr/
   [[:alpha:]]         # Start with a letter.
   (?:
      [[:alpha:]'-]+   # Allowed characters.
      [:alpha:]        # Don't end on a punctuation mark.
   )?                  # Catch single letter words.
/x;

##</code><code>##

my $last1;
my $last2;

while ($content =~ /($word)/g) {
   my $word = $1;

   ++$hash{               $word };
   ++$hash{       "$last1 $word"} if defined $last1;
   ++$hash{"$last2 $last1 $word"} if defined $last2;

   $last2 = $last1;
   $last1 = $word;
}