To include a condition, ala %IF%
TMPL:P already supports
conditions. It is very hard to work out the semantics for any more complex if expressions, as template definitions are expanded when they are loaded (hence the "TMPL:" part of the name), and there is no control over when
they are loaded (they may be cached from a previous load, for example). Therefore TMPL: expressions have to be evaluated statically. Even
is extremely dodgy. You certainly can't assume any variable definitions, you can't assume and URL params. If you want to use these in the condition, you might as well use %IF.
In fact, I think this should be remove context conditionals from TMPL:P, so that templates can be cached