Reformatted for for red-black tree in Perl 6

gistfile1.pl

enum RedBlack <R B>;
 
sub MAIN {
    my $tree = Any;

    for (1..10).pick(*) -> $node {
        $tree = insert($node, $tree);
        printf "%2d: %s\n", $node, $tree.perl;
    }
}
 
multi insert( $node, $tree ) {
    [B, ins( $node, $tree )[1..3]];
}

multi ins( $node, Any:U ) { [R, Any, $node, Any] }

multi ins( $node, @tree [RedBlack $color, $left, $pivot, $right] ) {
    when $node before $pivot { balance $color, ins($node, $left), $pivot, $right             }
    when $node after  $pivot { balance $color, $left,             $pivot, ins($node, $right) }
    default                  { @tree }
}
 
multi balance(RedBlack $color, $a, $x, $b) { [$color, $a, $x, $b] }

multi balance(B, [R, [R,$a,$x,$b], $y, $c ], $pivot, $right ) {                                                                                                                    
    [ R, [B,$a,$x,$b],        $y, [B,$c,$pivot,$right]] 
}
multi balance(B, [R, $a, $x, [R,$b,$y,$c] ], $pivot, $right ) {
    [ R, [B,$a,$x,$b],        $y, [B,$c,$pivot,$right]] 
}
multi balance(B, $left, $pivot, [R, [R,$b,$y,$c], $z, $d]  ) { 
    [ R, [B,$left,$pivot,$b], $y, [B,$c,$z,$d]]
}
multi balance(B, $left, $pivot, [R, $b, $y, [R,$c,$z,$d] ]) {
    [ R, [B,$left,$pivot,$b], $y, [B,$c,$z,$d]] 
}