condition - Regex to apply two lookbehind criteria -

I have a list of lowercase words on different lines, I want to match those lines in which the letter 'R' Where 'E' (er) is not before 'FO' (for).

Here is a sample list:

These are the words that I want to match:

  rejected Forrest fourteen  

These are two regexes, each half of what I want to do:

  ^. (* ((? & Lt;! E) r). *) $ ^ (. * (R (? Lt ;; fo) r). *) $  

'Something First match of all words except '; All other words except 'fortnight', so I want the words to match. Although in those words which are 'for' and 'er', any other matches with 'r' also. Applying a regex after the second fails to eliminate false positives.

How can I add two regexes with another condition, so that both are applied in an expression?

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You use a simple change

  ^ \ w * (? & Lt;! E | fo)? For example, http:  
  What does this do?   
  (? & Lt;! E | fo)  claims that regex to  e  or  fo  
 
  not defined by  match character  r  
 
 will match regex 
 
  Fourteen Rejects