Apache Velocity $ vs $!{}

For apache velocity, is there a difference between accessing va开发者_开发问答riables with $ vs. $!{}. If so, what is it?

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There's two differences, the second is formal and quiet.

Formal reference notations include the braces around the variable. The quiet notation includes the ! and means to output nothing if the reference does not exist. When combining them, you create a formal and quiet notation.