query: 
        { $stack->push(); $global->set("alias",0) } SELECT * from join { $stack->pop(undef) } ;

join:
       { $stack->push() }      
       table_or_join 
       { $stack->set("left",$stack->get("result")); }
       LEFT JOIN 
       table_or_join 
       ON 
       { $prng->arrayElement($stack->get("left")).".`int_key` = ".$prng->arrayElement($stack->get("result")).".`int_key`" }
       { $stack->pop([keys %{{map {$_=>1} (@{$stack->get("left")},@{$stack->get("result")})}}]) } ;

table_or_join:
        table | table | join ;

table:
       { $stack->push() } tab AS { my $x = $global->get("alias"); $global->set("alias",$x+1); $stack->pop(["alias$x"]); "alias$x" } ;

tab:
        A | B | AA | BB ;