Is it just an issue of file permissions, perhaps?  The line:

    Couldn't open >/tmp/.cpan/histfile: Permission denied

seems to indicate that you simply can't write to the file "histfile" in your .cpan directory.

Please check both the ownership and permissions of the file and its parent directories, with these commands:

  [myname@somehost ~]$ ls -ld /tmp
  [myname@somehost ~]$ ls -ld /tmp/.cpan
  [myname@somehost ~]$ ls -l  /tmp/.cpan/histfile
[download]

It's likely a fix as easy as something like:

  [myname@somehost ~]$ chown -R /tmp/.cpan `whoami`
  [myname@somehost ~]$ chmod -R u+rwx /tmp/.cpan
[download]