kyoshu,
I meant to respond to this earlier but I got busy and assumed someone would say the same thing anyway. Since you have a hardcoded file name and aren't using user data to construct it, you are more safe than you would have been otherwise. It is up to you to figure out if writing/appending to a file is safe or not.

In otherwords, if the file they are writing to is executed then it is very dangerous. This doesn't have anything to do with File::Slurp though. There are a myriad of reasons it might be dangerous to allow the write without checking it first but that's for you to decide. If you want to tell us how the data that is written to the file is used, we might be able to list all kinds of evil things you might want to check for.