Setup haproxy to proxy two apps by path

haproxy.cfg

global
  maxconn 4096
  user haproxy
  group haproxy
  daemon
  node lb1
  spread-checks 5

defaults
    log             global
    mode            http
    option          dontlognull
    retries         3
    option          redispatch
    maxconn         2000
    contimeout      5000
    clitimeout      50000
    srvtimeout      50000

frontend web
  bind :80
  mode http

  acl want_app1 path_dir app1
  acl want_app2 path_dir app2

  use_backend app1 if want_app1
  use_backend app2 if want_app2

backend app1
  mode http
  option httpclose

  reqirep ^([^\ ]*)\ /app1/([^\ ]*)\ (.*)$       \1\ /\2\ \3

  rspirep ^(Location:)\ http://([^/]*)/(.*)$    \1\ http://\2/app1/\3

  option httpchk GET / HTTP/1.0\r\nUser-Agent:\ HAProxy

  server app1_1 0.0.0.0:81

# the following backends follow the same pattern
backend app2
  mode http
  option httpclose

  reqirep ^([^\ ]*)\ /app2/([^\ ]*)\ (.*)$       \1\ /\2\ \3

  rspirep ^(Location:)\ http://([^/]*)/(.*)$    \1\ http://\2/app2/\3

  option httpchk GET / HTTP/1.0\r\nUser-Agent:\ HAProxy

  server app2_1 0.0.0.0:82