What is taint mode (-T) in Perl?

Taint mode (-T) in Perl is a security feature that helps prevent security vulnerabilities, particularly when dealing with user input. When taint mode is enabled, all data derived from user input is marked as "tainted," meaning that it cannot be used to affect the program's execution unless it is explicitly untainted.

In taint mode, Perl will raise an error if you attempt to use tainted data in a potentially dangerous way, such as accessing a file or executing a command. This can help ensure that user input is properly validated and cleaned before it is used in the program.