Replace every instance of 'aaa' with 'xaaax'.
aaa aab abb bbb aaa aab abb bbb aaa aab abb bbb aaa aab abb bbb aaa aab abb bbb
xaaax aab abb bbb xaaax aab abb bbb xaaax aab abb bbb xaaax aab abb bbb xaaax aab abb bbb