While I agree that there can be pitfalls to parsing, most of the time it isn't as bad as this. The "test" or "[" program has a unique challenge in that it never

While I agree that there can be pitfalls to parsing, most of the time it isn't as bad as this. The "test" or "[" program has a unique challenge in that it never gets to see the quotation marks or variable references, because the shell already expanded them. So when test sees that one of its arguments is the string "-f", it has no way to know whether that string came from a variable like $var, a quoted string literal like "-f", or just the text -f. Most of the time if you're writing a parser for your own DSL you don't have this problem. You can tell the difference between the string literal "+" and the operator +.