/
  (?:         # non capture group start
  ftp:\/{2}   # ftp://
  )?          # end optional non-capture group
  (?:         # non capture group start
  .*?\/       # anything non-greedy, followed by a /
   ){5}       # end non-capture group, match five times
  (.*?)       # capture everything, non-greedy
  \/          # until the very next fwd slash
/x