How to block specific User-Agent in ASM Policy

when HTTP_REQUEST {
    # Check if the User-Agent header contains "curl"
    if {[HTTP::header exists "User-Agent"] && [string tolower [HTTP::header "User-Agent"]] contains "curl"} {
        log local0. "Blocked request with User-Agent: [HTTP::header "User-Agent"] from IP: [IP::client_addr]"
        # Send an HTTP 403 Forbidden response
        HTTP::respond 403 content "Access denied."
        return
    }
}