// List concatenation. This procedure is just an example, the standard
// library "cat" is implemented in C.

// [1 2 3] [4 5 6] cat => [1 2 3 4 5 6]
[(a b)
    $b [$a -> (a)] foreach
    $a
] 'cat def

[1 2 3] [4 5 6] cat
showstack