Error on acl and backend

Hi to all, i have an installation of HAproxy 2.4.22 on ubuntu 22.04LTS (package from distro rep) i succesfuly deployed on production this installation with maps for choosing backend based on host from the request… now i have implemented an acl based on src file

    log global
    acl whitelist src -f /etc/haproxy/maps/ip_auth.lst
    option                  http-ignore-probes
    mode http

and then i put the code for the map file if whitelist else another map file

use_backend %[base,map_beg(/etc/haproxy/maps/] if whitelist
use_backend %[req.hdr(host),lower,map_reg(/etc/haproxy/maps/]

This config dosent play well the ACL is correctly triggered (i can see the acl apllied in the log) but the map is ignored. Someone could help me explaining why dosent work? for me it seem correct. Thanks in advance.