According to Damian Conway (master of most things related to bless and a whole lot of things that aren't), it's legal to bless a tied hash into an object.

However, your method doesn't look quite right. You create an anonymous hash, assign its reference to a scalar, and then dereference and bless it. In theory, that should work, but you'll have to do two layers of indirection when trying to get at the tied hash. I think something like the following is more in line with what you want. (Disclaimer: I haven't tried this, and I've never used Apache::Session, but it's a little cleaner.)

sub new {
    my $class = shift;
    my $id = shift;
    my %h = ();
    tie %h, 'Apache::Session::MySQL', $id {
        # whatever goes here
    };
    return bless(\%h, $class);
}
[download]