Executable XML users challenge

provide any LISP macro with clear explanation of its structure and function
that is :
1.concise (max 10 lines)
2.does not have a C equivalent(at least not anything above 100 lines)
3.does not use any libraries or imported complex functions which are not in C
If you provide an exact explanation/commentary on what it does i'll try to make a C solution which
is equivalent to LISP one. If i fail to do so, LISP wins, if i provide a solution you can make another macro.
If all examples in the thread are provide with C equivalents, LISP loses.

The process of reversing a string of text and sending it to compiler again is not complex either.
You just reverse a string of text, print it to file, and compile it.
Except it won't compile. Since reversing code will not be viable in C(C has real syntax, not textual soup of random words)and i can't find any practical example for the useless function i outlined above, and thus this code would not need to be written at all.