Description:
------------
See test-script. When I make the recursive-backreference (?R) optional (with ?) it doesn't match $str to its full extent.

Test script:
---------------
<?php
  $str = "A{X|param:{Y}}B";
  $reWanted =   '/{[A-Z]+(\|param:[^|}]*(?R)?[^|}]*)*}/';
  var_dump(preg_match($reWanted, $str, $m), $m);
  $reWorking =  '/{[A-Z]+(\|param:[^|}]*(?R)[^|}]*)*}/';
  var_dump(preg_match($reWorking, $str, $m), $m);
  $reWorking2 = '/{[A-Z]+(\|param:([^|}]*(?R)[^|}]*|[^|}]*))*}/';
  var_dump(preg_match($reWorking2, $str, $m), $m);
?>

Expected result:
----------------
For all three cases:

int(1)
array(3) {
  [0]=>
  string(13) "{X|param:{Y}}"
  [1]=>
  string(10) "|param:{Y}"
  [2]=>
  string(3) "{Y}"
}


Actual result:
--------------
Using $reWanted gives this instead of the expected result. Note the missing }

int(1)
array(2) {
  [0]=>
  string(12) "{X|param:{Y}"
  [1]=>
  string(9) "|param:{Y"
}