[exim] question about exim filters

dear sirs

i have little question about the exim filters
which is....can i use variables $domain and $local_part inside the filter??

i have a situation where i use maildir filesystem and the inbox path of the user is /var/mail/$domain/$local_part/mail

now i want to make a filter (or even a router) that according to some header detected "like spam score for example" i want it to put the message inside /var/mail/$domain/$local_part/mail/.Bulk

note: all the files for all users and domains is the same USER: exim and the same GROUP:mail

thanks
mostafa