This is a template to demonstrate recursive macros!

Macros can have arguments that contains macros. For
example:
    This is an apple

If the macro argument can be resolved at parse time it is done
so. But if not the resolution of the whole macro will be
left to the end.

Now to get to the real recursive macros. In the Example3 we
saw the INCLUDE macro that did that. Here we'll define
two macros (GIRLS and BOYS) and GIRLS is the recursive
macro that returns an instance of BOYS:
    Girls like icecream, but boys like icecream too. Ahem!

Some macros are not recursive. One of those is the KEY
macro, lets try to replace into KEY a macro:
    Key contents - <!--GIRLS:flowers-->

So recursive macros are macros that post-parse their output
and look for additional macro tags. Recursive macros
include:
    INCLUDE
    ALIAS

Non-recursive:
    KEY and family

If a recursive macro contains SUB-s they are parsed only
if the macro is expanded on parse time. If macro output
contains subs at outputing time the system will post
a complaint to TemplateContext and the contents of SUBS
will be discarded.