ACL for rate limiting when rate greater than value in http-request variable

I am trying to load up rate limits from a map file (which works), and then apply those rate limits to the request.

I have loaded up my rate limit to apply into txn.applied_rate_limit_by_ip, but when I try to use this variable in the “gt” comparision operator, I get a syntax error.

example acl:
acl req_rate_abuse_gr_service sc_http_req_rate(0) gt txn.applied_rate_limit_by_ip

error detected while parsing ACL 'req_rate_abuse_gr_service' : 'txn.applied_rate_limit_by_ip' is neither a number nor a supported operator.

I’ve tried numerous things to convert this to “a number” such as the following, with no luck:

is it possible to make this work and use a dynamic right side of the “gt” operator?

I also tried defining a lua.greater_than function and calling it from the same acl line, with similar issue.