Apache rewrite rule equivalent

Help!
1

Hi there, how would this Apache rewrite rule translate to HAProxy?

RewriteCond "%{QUERY_STRING}" !hint 
RewriteRule "endpoint/o/authz" "/endpoint/o/authz?hint=xyz" [QSA,PT]

I tried the following, but it does not seem to work.

acl is_not_hint path_reg !-m /endpoint/o/authz?hint
http-request replace-path /endpoint/o/authz?(.*) /endpoint/o/authz?hint=xyz\1 if is_not_hint

Any insigth will be appreceiated. Thanks!