Se você dividir um frontend http, isso pode simplificar as coisas
frontend http_in
bind *:80
redirect prefix https://www.example.com code 301
frontend https_in
all www.example.com hdr_sub(host) www.example.com
bind *:443 ssl crt /etc/haproxy/certificate.bundled.pem
redirect prefix https://www.example.com code 301 if !www.example.com
...