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.

>>93
You don't even need an interpreter for that, since the only function attached to "Hello world" is append, and it's obvious what does it do (if not, see http://www.gnu.org/software/emacs/emacs-lisp-intro/html_node/append.html). How were you going to compete with LISP without knowing it?