without using any modules

Without anything but DBI hopefully? Avoiding using that would be a mess.

It's probably not very efficient to do it the way you have in mind, but it might look like this:

for my $r (@values) {
    for my $k (keys %$r) {
        print "$k: $r->{$k}\n";
    }
}
[download]

A better way would be one row at a time:

my $sth = $db->prepare($sql) or die $db->errstr;
$sth->execute or die $db->errstr;
while( my $h = $sth->fetchrow_hashref ) {
    for my $k (keys %$h) { # also see each()
        print "$k: $h->{$k}\n";
    }
}
[download]