Macro kk 

macro_rules! kk {
    ($e:expr) => { ... };
    ($($arg:tt)*) => { ... };
}

kk! is to used to expand the inner tiles, by keeping the white spaces (i.e. do not trim any white spaces around the block) and return a tile

use rtile::prelude::*;

kp!(numbers, "     1, 2, 3, 4, 5     ");
let mut result = kk!("  Numbers: @{numbers}  ");
kp!(numbers, "   one, two, three, four, five   ");
result |= k!("  In words: @{numbers}  ");
assert_eq!(result.to_string(), ks!("  Numbers:      1, 2, 3, 4, 5       \n  In words:    one, two, three, four, five     "));