Boolean Operator in Pandoc Template

Pandoc Template supports if-clauses and for-loops. For example,

$if(foo)$
part one
$else$
part two
$endif$

How to do boolean logic inside the if-clause argument? For example,

$if(foo AND bar)$
both
$endif$

and

$if(foo OR bar)$
both
$endif$

The template language has no support for this. Boolean AND can be simulated by using two ifs.

$-- foo AND bar
$if(foo)$
$if(bar)$
both
$endif$
$endif$

Boolean OR is not really possible though; the best method would be to use a partial to avoid too much repetition:

$-- foo OR bar
$if(foo)$
$my.partial()$
$else$
$if(bar)$
$my.partial()$
$endif$
$endif$

It is often easier to move the calculations to a (Lua) filter for even mildly complicated logic.

function Meta (meta)
  meta['foo-and-bar'] = meta.foo or meta.bar
  return meta
end

Drawback: if foo or bar are not part of the metadata but of the set of variables, then this won't work, as filters don't have access to variables. Use a custom writer in that case.