Currently, compile options can be set by RubyVM::InstructionSequence.compile_option=. However, it takes effect only on code compiled after the options are set. So, how about to add new magic comments for compile options? For example, the following code sets the options tailcall_optimization and trace_instruction. ```ruby # -*- tailcall-optimization: true; trace-instruction: false -*- def fact(n, i = 1) if n == 0 i else fact(n - 1, n * i) end end p fact(10000) ``` With the attached patch, magic comments in the main script sets global options, and magic comments in a required library are effective only in that library.