Mapping domains and subdomains

HA v. 2.4.12

use_backend %[hdr(host),lower,map_dom(/etc/haproxy/Maps/] srv srv1 srv3

Now, calling only matches the first occurrence of map ‘
What would be the right syntax for an exact match? map_beg, map_end or map_str ?

Also wonder, whether can point to multiple map files (due to better organization) at same front end?