Today I had a task which sounded like this "Change for balancer urls for this VIP - vip:8080 -> server* 16081/int"

Long story short:

frontend my_vip
     bind x.x.x.x:8080
     mode http
     maxconn 30000
     default_backend my_backend

backend my_backend
     mode http
     balance leastconn
     acl int_prefix path_beg /int
     reqrep ^([^\ :]*)\ /(.*) \1\ /int/\2 unless int_prefix
     server server1 y.y.y.y:16081 maxconn 32 check fall 3
     server server2 z.z.z.z:16081 maxconn 32 check fall 3