require 'pp'

def doit(str)
  grant_regex = '
    ([^@]+)       (?# user)
    @
    ([^\/]+)      (?# host)
    (
      \/([^,]+)   (?# database)
      (
        ,(\S+)    (?# tables)
      )?          (?# tables are optional)
    )?            (?# database and tables are optional)
  '

  matches = Regexp.new(/^#{grant_regex}$/x).match(str).captures.compact
  matches.delete_at 2
  matches.delete_at 3
  pp matches
end

doit "pitc_puzzletime@10.2.%.%"
doit "pitc_puzzletime@10.2.%.%/pitc_puzzletime_prod"
doit "pitc_puzzletime@db-host.puzzl.ch/pitc_puzzletime_prod,diese_tabelle,andere_tabelle"