These are all examples of arbitrarily nested loops in p6
For details, see http://perlmonks.org/?node_id=462987 

For example:

LoopOver( ([1..3], ['a'..'z'], ['foo', 'bar']) );

Where LoopOver needs to figure out dynamically

for 1..3 {
    for 'a'..'z' {
        for <foo bar> {
           ...
        }
    }
}