Owl is one of the main user of those operators (which is expected since they were introduced with numerical libraries in mind) in particular to get a lighter syntax for slicing: Slicing and Broadcasting - Owl Online Tutorials .
For instance, the linked tutorial provides an example for zeroing a slice of an array:
let x = sequential [|10; 10; 10|] in
let a = x.${[0;4]; [6;-1]; [-1;0]} in
let b = zeros (shape a) in
x.${[0;4]; [6;-1]; [-1;0]} <- b