X metaop

```perl6
(Model1.^all X Model2.^all).grep: { .[0].col1 == .[1].col2 }
```

should it do something like this?

```sql
SELECT
   table1.*, table2.*
FROM
   table1 as t1
   JOIN table2 as t2 ON t1.col1 = t2.col2
```