note JohnN <p>I have a dumb question.</p> <p>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}</p> e.g.<br> <code> /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; </code> <p>versus</p> <code> /CCGG ( (?: (?!CCGG) . ){50,100}? # <==== ) AATT # and ending at AATT /x; </code> <p>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.</p> <p><b>A follow-up:</b> The following code snippet fixes my problem, and I have NO idea why! I tried it out of desperation</p> <code> /CCGG ( (?: (?!AATT|CCGG) # <============= . # ){50,100}? # Here the "?" is not required but I'm anal ) # AATT # /x; </code> 518444 911397