It's not a case of your password or your system or any password or system in particular. Remember, perl is a general purpose tool, used by many people in many situations, and the tainting mechanism is designed to help protect everyone who uses it.

It works like this. If data (string, numbers, filenames, whatever) comes into your program from an external source, then, when you use -T, you are asking perl to warn you when you try to use that data in a way that could be dangerous in some situations, until you untaint it.

Untainting, means using a regex to inspect and modify the contents of that data. At this point, perl says "Okay. You got data from an external source, you've 'edited it', I cannot predict what type of editing is required to make that data safe, so I must assume that you--the programmer--know what you are doing, so now I will let you use that edited data in whatever way you want!".

In other words. You asked perl to tell you when you attempted to do something dangerous with external input. It did. Now it is up to you to take those steps to untaint the data in whatever way you believe will make it safe.

The risk is yours to access and the steps are yours to take.