Others have provided answers to what you should have asked, but I'll answer what you really asked. The answer is that qr// creates a precompiled regexp with all the modifiers set. So when you create $np, you need to specify the /ms there. If you were to print out $np, you'd see that it starts with (?x-ism:, meaning that it overrides any modifiers you specify later on (so that it has its own self-contained meaning).