Select Code to Download

my $first = "the";
my $last = "dog";
my $string = "The black dog danced around the sleeping dog."
my @matches = $string =~ m/\b($first\b(?!.*?$first.*?)\b$last)\b/g;

my $first = "the";
my $last = "dog";
...
# The black dog
# the sleeping dog
# the lazy dog