This notation can be seen made use of in equation 1.5 of https://arxiv.org/pdf/1311.5200.pdf
Roughly speaking, $$\left. I = \int f(z) \prod_a \frac{dz^a}{z-z_a} \middle/ d\omega \right.$$ where $$d\omega = \frac{dz^1 dz^2 dz^3}{(z-z_1)(z-z_2)(z-z_3)} $$I do not understand what this slash notation means. Any examples will be greatly appreciated.