regex - in a file?

Hi,

We are thinking of having multiple regexes.  Below is simlar to what
we currently have.

# deny messages matching a particular regex not in our network
deny  message = This message matches a blacklisted regular expression ($regex_match_string)
      condition = ${if <{$message_size}{20k}{1}{0}}
      regex = http.//4drugs123.com : etc : etc2

The problem that we have now is that the regex string is getting very
long.  Not only so, continually modifying the exim.conf file is not
feasible for us.

Is it actually possible to have the 'regex' read from a file?   We
tried using lsearch, and it seems that the regex line is not able
to understand that?  Or did we make a syntax error somewhere?

Thanks for the Help,

Lawrence