[Exim] how to accept a regular expression on the entire reci…

So far, my exim.conf had authenticated all senders and applied the default

rules otherwise.
acl_check_rcpt:
  accept  hosts = :
  deny    local_parts   = ^.*[@%!/|] : ^\\.
  accept  authenticated = *
  deny    message       = relay not permitted

now I want to also allow address with a given prefix (e.g. "rrr") and then
3-10 hexadecimal character and no domain part. Unfortunately, the below
fails with <<LOG: PANIC DIE
Exim configuration error in line 45:
error in ACL: unknown ACL condition/modifier in "accept...>>

acl_check_rcpt:
  accept  hosts = :
  accept recipient = ^rrr[a-zA-Z0-6]{3,10}$
  endpass
  deny    local_parts   = ^.*[@%!/|] : ^\\.
  accept  authenticated = *
  deny    message       = relay not permitted

Any help would be highly appreciated since I couldn't figure it out reading
http://www.exim.org/exim-html-4.20/doc/html/spec_7.html and
http://www.exim.org/exim-html-4.20/doc/html/spec_37.html!

    Ralf