HAProxy ACL Regex Rules

HAProxy ACL Regex Rules
Official Website about append-slash
http://cbonte.github.io/haproxy-dconv/1.6/configuration.html#4.2-redirect%20scheme
Recently, there is an issue about URL proxy
https://www.sillycat.com/blog/free-google-ads-adwords-coupon-codes/
From server side, both URLs are working
https://www.sillycat.com/blog/free-google-ads-adwords-coupon-codes
https://www.sillycat.com/blog/free-google-ads-adwords-coupon-codes/
But for google SEO, they will index 2 times which my boss thinks it is not good.
One option is to remove the blash in following configuration
frontend webapp
    bind *:80
    bind *:443
    http-request redirect code 301 location http://%[hdr(host)]%[url,regsub(/$,)] if { path_end / } { path_len gt 1 }
But that breaks some of the blog pages with requires / in the end.
So we choose another option add blash all the time.
    acl is_root path -i /
    acl missing_slash path_reg [^\/]$
    acl function_suffix path_reg \.[a-zA-Z]{3,4}
acl host_community_sillycat    hdr_dom(host) -I community.sillycat.io
acl host_static_sillycat        hdr_dom(host) -I www.sillycat.io
acl host_sillycat                 hdr(host) -i sillycat.io
    http-request redirect code 301 prefix / append-slash if missing_slash !function_suffix !is_root host_community_sillycat
    http-request redirect code 301 prefix / append-slash if missing_slash !function_suffix !is_root host_static_sillycat
    http-request redirect code 301 prefix / append-slash if missing_slash !function_suffix !is_root host_sillycat

Command line to verify if it works
> curl -I https://www.sillycat.io/blog/free-google-ads-adwords-coupon-codes
HTTP/1.1 301 Moved Permanently
Content-length: 0
Location: /blog/free-google-ads-adwords-coupon-codes/

References:
http://www.voidcn.com/article/p-uezxokfw-em.html
https://github.com/ehazlett/interlock/blob/master/ext/lb/haproxy/template.go
https://stackoverflow.com/questions/47860773/haproxy-routing-based-on-url
https://github.com/vfarcic/docker-flow-proxy/issues/390
https://serverfault.com/questions/847599/haproxy-request-rewrite
https://discourse.haproxy.org/t/remove-the-trailing-slash/2278/16