Well I found a solution, now the metric name reside in variables $0 $1 $2 … $n , while it is basically expanded metric name by dot character separator.
Example metric fetched via /^netdata.apps.pwrites.*/ :
netdata.apps.pwrites.sql is expanded as:
$0 - netdata
$1 - apps
$2 - pwrites
$3 - sql
So in my case I can use $3 in Alias field 