Flasm is a command line assembler/disassembler for SWF bytecode.
You can use it for low-level optimisations or to manually obfuscate your algorithms for some protection against decompilers. By disassembling simple SWFs you can also gain valuable insights into the inner workings of the Flash Virtual Machine, which is also well explained on the Flasm website.
Flasm, documentation and other information can be found at http://www.nowrap.de/flasm.
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