1. Take the worse from S-expressions.
{spoiler {b YOU SAID THE PARENTHESES, RIGHT, ``FAGGOT''?}}
2. Now take away the parens, add angle brackets, superfluos closing tags, unnecessary verbosity and remove types (lists, symbols, numbers, strings, who will ever need them!).
3. Add an even more verbose XSLT that transforms the tree in something else for {b.u.i.o ENTEPRISE REVOLUTIONARY METAPROGRAMMING}.
4. <root>You've got xml! Enjoy your <bbcode tag="code"><integer>5</integer></bbcode>, or <bbcode tag="code"><atom type="integer">5</atom></bbcode> and <bbcode tag="code"><apply operator="+"><list typed="false"><atom type="integer">1</atom><atom type="integer">2</atom><atom type="integer">3</atom></list></apply></bbcode> instead of <bbcode tag="code">(apply + '(1 2 3))</bbcode><bbcode tag="i">!</bbcode></root>