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.

>>13
In some cases you may want to compile and load dynamically object files like tiny .dll's or .o files into the parent process executable space,
but they all require calling the compiler at least once(to produce the executable object file: it may be even 1 function long).
Anyway i've not seen any clear example of LISP macro which does something exclusive to LISP, so i could compare and propose an equivalent(which could even not use regexes or some complex features, just C code).