In the current working draft of XQuery F&O 3.0, the fn:for-each() function ( http://www.w3.org/TR/xpath-functions-30/#func-for-each ) has the following equivalent XQuery code:

declare function fn:for-each($seq, $f) {
  if (fn:empty($seq))
  then ()
  else $f(fn:head($seq)), fn:for-each(fn:tail($seq), $f)
};

Probably the parenthesis around the else branch have been omitted, and so this code will result in an infinite recursion for any input. The fix would be to change the line:

  else $f(fn:head($seq)), fn:for-each(fn:tail($seq), $f)

to: 

  else ($f(fn:head($seq)), fn:for-each(fn:tail($seq), $f))