Math can be applied directly to variable values.
数学运算可以直接应用到变量
{$foo+1}
{$foo*$bar}
{* some more complicated examples *}
{$foo->bar-$bar[1]*$baz->foo->bar()-3*7}
{if ($foo+$bar.test%$baz*134232+10+$b+10)}
{$foo|truncate:"`$fooTruncCount/$barTruncFactor-1`"}
{assign var="foo" value="`$foo+$bar`"}