在Perl中,如何处理整个哈希？

my %hash = (key1 => 'value1', key2 => 'value2', key3 => 'value3');

foreach my $key (keys %hash) {
    my $value = $hash{$key};
    print "Key: $key, Value: $value\n";
}

my %hash = (key1 => 'value1', key2 => 'value2', key3 => 'value3');

foreach my $value (values %hash) {
    print "Value: $value\n";
}

my %hash = (key1 => 'value1', key2 => 'value2', key3 => 'value3');

foreach my $key (keys %hash) {
    print "Key: $key\n";
}

my %hash = (key1 => 'value1', key2 => 'value2', key3 => 'value3');

while (my ($key, $value) = each %hash) {
    print "Key: $key, Value: $value\n";
}

my %hash = (key1 => 'value1', key2 => 'value2', key3 => 'value3');

my %new_hash = map { $_ => length($hash{$_}) } keys %hash;

print "New hash: ", Dumper(\%new_hash);