# original QL code:
my $ql_code = 'select object() from Foo::Bar';

# parsed into something like this 
my $ast = [ select => [ 'object' ], [ from => 'Foo::Bar' ]]

# create the query db
my $query_db = DBM::Deep->new;

$query->{$ql_code} = $ast;

##</code><code>##


# assuming the query above
# the compiled sub might look
# something like this
sub {
    my $query_engine = shift;
    return $query_engine->select(
        'object', 
        $query_engine->from('Foo::Bar')
    );
}