It helps to debug typo mistakes (language independent). If you was doing a regular compare '==' but used '=' instead, then 'wait = -1' will assign -1 to wait which could cause run time problems later on. However, if you do '-1 = wait' the compiler will throw a syntax error because you are trying change a constant.
Good point, except you "can't modify wait in scalar assignment" either, or atleast that's what perl says when I try. For variables though, I see what you mean.
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Time flies when you don't know what you're doing