use strict; use warnings; use feature 'say';
use Data::Dumper; $Data::Dumper::Sortkeys = $Data::Dumper::Indent = 1;

my $href = {
    cat => { milk => 1 },
    dog => { bone => 1 },
};

say exists $href->{'cow'} &&
    exists $href->{'cow'}->{'alfalfa'} ? 'cow' : 'no cow';

say Dumper $href

__END__