Nullifies the result value returned by the execution of a script section or the resolution of an attribute.
pc:void is the counterpart of pc:evaluate, which does return the result value.
The content of pc:void is executed without result value. The content of pc:defs is not executed at all.
You can use pc:void if you are interested in having an attribute resolved (as in the Example) but you are not interested in the return value.
You can use pc:void to surround a directive or an entire script section (a set of directives) that you want to suppress the result value of.
Often, you do not need to write pc:void explicitly. It is standard behaviour in USoft Blend that the return value of pc:copy-of is automatically suppressed if the script returns (also) other output.