HAProxy - Dynamic selection of backend based on subdomain

[planetinse]

I have a scenario where I basically repeat endless (>500) ACL's using following frontend input

sub1 > Custom acl > ssl_fc_sni -i sub1.domain.com
and then
use backend > sub1 > b_sub1

traffic is a secure websocket, so I terminate and loopback before doing the step above, ssl_fc_sni is only way to get host to my knowledge (and its working fine!)

I wonder if I can somewhat have a single line dynamic rule that connects to the correct backend using the subdomain value as part of the naming.