force rewrite of cookie

[Runozo]

Greeetings and thanks for Haproxy

I have the following backends configured and working with correct ACLs:

backend back1
        description balanced server apps
        mode http
        cookie SRV insert nocache indirect
        balance roundrobin
        option forwardfor
        option redispatch
        option http-server-close
        option tcp-smart-connect
        option httpchk HEAD /httpcheck.asp
        server www01-sia 192.168.41.235:80 cookie 1 maxconn 200 slowstart
30s weight 1 check
        server www02-sia 192.168.41.236:80 cookie 2 maxconn 200 slowstart
30s weight 1 check

backend back2
        description single server apps
        mode http
        # reqadd Cookie:\ SRV=1
        # reqidel ^Cookie:.*SRV=.*
        # cookie SRV insert nocache
        option forwardfor
        server www01-sia 192.168.41.235:80 maxconn 500 slowstart 1m check

Now, i wish that when the client is on "back2", the SRV client cookie be
always rewritten with value 1 so, when client come back to "back1" will be
sticked to server 1

Is it possible? I think yes, but cannot figure out how

Thank you all again,
Runozo