variables in AuthzSVNAccessFile - a shortcut?

[lejeczek]

hi everybody

as a novice I understand I'm looking for shortcuts, probably 
being not the first one I'd have this question:

does Subversion implement any variables in it's configuration?
first case to exercise this scenario would be AuthzSVNAccessFile
could one have

[REPO_NAME:/_$user]
_$user = rw

naturally I'm thinking here of login/logged in user, via http
many thanks.