I have a dumb question.

This code works well (THANKS Roy!) when looking for DNA string matches within a genome sequence but not when the * is changed to {50,100}

e.g.
/CCGG          # Match starting at DNA sequence CCGG
  (          
    (?:        
      (?!CCGG) #   make sure we're not finding duplicates mid-stream
      .             #   accept any character
    )*?            # any number of times BUT not greedily <====
  )          
  AATT         # and ending at AATT
/x;

[download]

versus

/CCGG   
  (          
    (?:        
      (?!CCGG)  
      .        
    ){50,100}?        # <====
   )         
  AATT  # and ending at AATT
/x;

[download]

This latter one does not have dupes of CCGG but does have dupes of AATT. The previous snippet has no dupes of either CCGG or AATT.

A follow-up: The following code snippet fixes my problem, and I have NO idea why! I tried it out of desperation

/CCGG   
  (          
    (?:        
      (?!AATT|CCGG) #     <=============
      .       # 
    ){50,100}?        # Here the "?" is not required but I'm anal
  )         # 
  AATT  # 
/x;

[download]

In reply to Re^4: Using Look-ahead and Look-behind by JohnN
in thread Using Look-ahead and Look-behind by Roy Johnson

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