OK, no file. So have you tried FTPing that file using any software other than this Perl script? e.g., since you're on Linux:

wget ftp://ftp.cpan.org/pub/CPAN/README.html

should be available and do basically the same thing as your script is trying to do. If wget isn't there, you can also try curl or ftp.

(Incidentally, I just tried this a couple times with wget, and had one mirror time out. Timing out... when using a known-good tool... which is the same way your script is failing... Interesting, no?)