如何在perl中使用变量作为正则表达式修饰符?

I'm writing an abstraction function that will ask the user a given question and validate the answer based on a given regular expression. The question is repeated until the answer matches the validation regexp. However, I also want the client to be able to specify whether the answer must match case-sensitively or not. So something like this:I'm writing an abstraction function that will a