// This is a commented version of the implementation of 'foreach' inside
// the standard library.

[(l f) // list and function to call with each element.
    $l len (e)  // Get list len in "e"
    0 (j)       // j is our current index
    [$j $e <] [
        $l $j get@  // Get list[j]
        $f upeval   // We want to evaluate in the context of the caller
        $j 1 + (j)  // Go to the next index
    ] while
] 'foreach def

[1 2 3] [printnl] foreach