[exim] Regex help

Hello,

i am not so familiar with regex, possibly someone
can help me.

Currently i use in the ACL section:

deny message = Use mobilenumber-robot@??? as recipient \n\
                i.e. 49179123456-robot@???
       condition = ${if eq{$local_part}{robot}{1}{0}}
       domains=test.archesoft.de

I am loking for a condition, that better checks valid
recipients.
- the first chars of the local_part should be numeric.
- the length of the numeric chars should be at least 8
- last chars of local_part should be '-robot'

I wasn't able to work out a workable regex to meet the 3 conditions.

Possibly you can send me an example of a similiar regex
or give me a link to some webpages.

Thanks,
Torsten