Hi,
I think I've spotted a bug in array:fold-left (using 20141219 snapshot)
array:tail([1,2,3]) => [2,3]
array:fold-left( array:tail([1,2,3]), (), function($result, $fn) { ($result, $fn) } )
=> (1,2)
Using array:fold-right in the above example returns (2,3).