in reply to IO::Tee problem (Well, problem with my brain, anyway)

Your code contains:
open my $read, '<', 'Fanggame.txt'; open my $write, '>>', 'Fanggame.txt';

That is, you open for input and appending for output the same file.

Every time you run the program, you should double the size of your input file. Run it again; how much longer does the file get?