Your post gives very little information to go on.
One possibility, however minor, is that the tarball you want to download is actually corrupt, even over there on CPAN.
Another blind guess is that your browser has decompressed the gzip compression (browsers have builtin support for it); and tar pads its metadata with blanks. But there should still be data inside the file, and if you rename it to just .tar you can still extract the files.
Or there might be an issue with your network connection; maybe theres a too-clever-by-half proxy somewhere in there, possibly a transparent one; or who knows what. Try downloading from a different CPAN mirror.
Makeshifts last the longest.
Can you tell us which modules you are downloading which are giving you this problem?
Are you familiar with uncompressing tar.gz files?
Martin
some: adj.
1. Being an unspecified number or quantity:
Some people will downvote this node.
Some people will just ignore this node.
Some people will point you to node 172086
Some people may even know what modules you're talking about
And some people will just start off the new year being smarmy