...
/c/ matches "c" (at position 3)
   /d/ matches "d"
      /.*/ matches " cd EF ghi jkl"
         /g/ fails -> backtrack
      /.*/ matches " cd EF ghi jk"
         /g/ fails -> backtrack
      /.*/ matches " cd EF ghi j"
         /g/ fails -> backtrack
      ...
      /.*/ matches " cd EF "
         /g/ matches "g"
            /h/ matches "h"
               /i/ matches "i" -> success

##</code><code>##

...
/c/ matches "c" (at position 3)
   /d/ matches "d"
      /.*?/ matches ""
         /g/ fails -> backtrack
      /.*?/ matches " "
         /g/ fails -> backtrack
      /.*?/ matches " c"
         /g/ fails -> backtrack
      ...
      /.*?/ matches " cd EF "
         /g/ matches "g"
            /h/ matches "h"
               /i/ matches "i" -> success

##</code><code>##

/cd(?:(?!cd|ghi).)ghi/s