m/
      ^  # beginning of line
      (?:\d?\d?\d\.\d?\d?\d\.\d?\d?\d\.\d?\d?\d) # pseudo IP address
        [ ] # delimiter
      (?:\S+|-)[ ](?:\S+|-) # second and third fields...
        [ ] # delimiter
      \[
         (?:[12][0-9]|3[01]|[1-9]) # date 10-19,20-29,30,31,1-9
            /
         (?:J(?:un|ul|an)|Feb|Ma(?:r|y)|A(?:pr|ug)|Sep|Oct|Nov|Dev) # month 
            /
         \d\d\d\d # year
            :
         (?:[01][0-9]|2[0-3]):(?:[0-5][0-9]):(?:[0-5][0-9]) # time
      \]
         [ ] # delimiter
      \d\d\d # HTTP code
         [ ] # delimiter
      (?:\d+|-) # bytes
         [ ] # delimiter
      "[^"]+" # HTTP request
         [ ] # delimiter
      "(?:[^"]+|-)" # referer
      $ # end
   /x;