use strict; 
use warnings; 
my %classification = get_rules(); 
my %who_is; 
foreach my $animal (keys %classification) { 
    push @{$who_is{$classification{$animal}}}, $animal; 
} 
while ( (my $question = prompt('Enter question ("exit" to quit): ')) ne 'exit') { 
     
    if ($question =~ /^What/){ 
        my $test = join '|', keys %classification; 
        my ($animal) = $question =~ /(:?$test)/; 
        if (!defined $animal) { 
            print "Your animal is not classified.\n"; 
            next; 
        } 
        print "$animal is $classification{$animal}.\n"; 
    } 
    elsif ($question =~ /^Who/) { 
        my $test = join '|', keys %who_is; 
        my ($catagory) = $question =~ /(:?$test)/; 
        if (!defined $catagory) { 
            print "Your catagory is not known.\n"; 
            next;  
 
        } 
        foreach my $animal (@{$who_is{$catagory}}) { 
            print "$animal is $classification{$animal}.\n"; 
        } 
    } 
     
    else { 
        print 'Question must start with "Who" or "What".', "\n"; 
    } 
}  
 
 
sub prompt { 
    print $_[0]; 
    my $response = <>; 
    chomp $response; 
    return $response; 
}  
 
sub get_rules { 
    my %classification; 
    while (my $rule = <DATA>){ 
        my ($animal, $catagory) = $rule =~ /\AAn?\s(\w+)\sis\san?\s(\w+)\.\s*\z/; 
        $classification{$animal} = $catagory; 
    } 
    return %classification; 
} 
__DATA__ 
A cat is a mammal.  
A dog is a mammal.  
A bluejay is a bird.  
A snake is a reptile.  
A lizard is a reptile.  
A frog is an amphibian.  
An owl is a bird.  
A carp is a fish.