$ perl -e '
    use Data::Dump;
    my %h = qw{cat Tibbles dog Rover kitten Tibbles};
    my %r = reverse %h;
    dd \%h;
    dd \%r;
'
{ cat => "Tibbles", dog => "Rover", kitten => "Tibbles" }
{ Rover => "dog", Tibbles => "cat" }

$ perl -e '
    use Data::Dump;
    my %h = qw{cat Tibbles dog Rover kitten Tibbles};
    my %r = reverse %h;
    dd \%h;
    dd \%r;
'
{ cat => "Tibbles", dog => "Rover", kitten => "Tibbles" }
{ Rover => "dog", Tibbles => "kitten" }