$ perl -Mstrict -Mwarnings -e '
    use List::MoreUtils qw{uniq};
    use Data::Dumper;

    my @pets = (
        { a => "cat", b => "dog" },
        { c => "dog", d => "cat" },
        { e => "dog" },
        { f => "cat" },
        { g => "goldfish" },
        { h => "cat", i => "cat" },
        { j => "cat", k => "cat", l => "dog", m => "dog" },
    );

    my @cat_and_dog;

    for (@pets) {
        push @cat_and_dog, $_ if 2 == grep { /^(?:cat|dog)$/ } uniq values %$_;
    }

    print Dumper \@cat_and_dog;
'
$VAR1 = [
          {
            'b' => 'dog',
            'a' => 'cat'
          },
          {
            'd' => 'cat',
            'c' => 'dog'
          },
          {
            'j' => 'cat',
            'k' => 'cat',
            'l' => 'dog',
            'm' => 'dog'
          }
        ];