my %foo;
my $string = 'Poet Blake had a milky white cat. He used to call it Pussy.';
for my $word (split /\s+/, $string) {
   $foo{$word}++;
}

##</code><code>##

my $cnt;
for my $word (keys %foo) {
    $cnt++ if $bar{$word};
}

##</code><code>##

my $word_count = scalar keys %foo;