my %SWITCH = (
   CAT      => 0b00001,
   DOG      => 0b00010,
   HAMSTER  => 0b00100,
   FERRIT   => 0b01000,
   FISH     => 0b10000);
   
my $petInput = 2;
my @PETS;

for ( keys %SWITCH ) {
  push @PETS, $_ if $SWITCH{$_} == $petInput;      
}

print "$_\n" for @PETS; # DOG