You don't really need a command module for this, but the memory is very limited. There is a small 100-byte buffer that holds the bytecode instruction stream.
在这种情况下，您并不需要一个命令模块，但是内存容量十分有限，其大小只有100个字节。
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You might replace an XPath expression, an instruction, a template, or an imported stylesheet module, among other constructs, and the replacement might be a different granularity.