title: how to regex 2 char by 2 char
body: <p>Edited question because it was misunderstood.</p>
  
  <p>Ex : I own these two strings of 5 pairs :</p>
  
  <p>Line 1 : 0102030405</p>
  
  <p>Line 2 : 0102203035</p>
  
  <p>and I want to find 01 and 02 and 03 (for example) ; the expected result is :</p>
  
  <p>matches : <strong>010203</strong>0405</p>
  
  <p>does not match : 0102203035</p>
  
  <p>And if I want to find 01 and 02 and 30 (for example) ; the result I want is :</p>
  
  <p>does not match : 0102030405</p>
  
  <p>matches : <strong>0102</strong>20<strong>30</strong>35</p>
  
  <p>Each pair is in a position modulo 2 (of course)</p>
  
  <p>What regex pattern can I use ?</p>
  
  <p>Thank you for the help !</p>