#!/bin/bash s='1.15.2.119 1.15.86.33 1.15.251.60 1.20.178.145/31 1.37.33.24 1.54.202.216 1.58.10.126/28 1.80.225.84 1.116.240.174/30' sed '\,/,!s,$,/32,' <<< "$s"
Standard input is empty
1.15.2.119/32 1.15.86.33/32 1.15.251.60/32 1.20.178.145/31 1.37.33.24/32 1.54.202.216/32 1.58.10.126/28 1.80.225.84/32 1.116.240.174/30