• Forget about LWP::Simple. You seem to cope with LWP::UserAgent fine.
• Use LWP::Simple, and have it export $ua. Set up the proxy through $au, as in your code (But the method above is just as easy).
• Either use LWP::UserAgent or LWP::Simple as described above, and setup the proxy using environment variables and a call to $au -> env_proxy.

Abigail

Step two above is exactly what I wanted but I wasn't quite sure exactly what was required but I am now so for others for future reference:

   # use proxy (comment out if not)
   my %proxy = ( host => 'http://proxy:8080' );

   use LWP::Simple qw(mirror RC_OK RC_NOT_MODIFIED $ua);

   $ua->proxy(http => "$proxy{host}") if (defined $proxy{host});
[download]

You can see I'm just interested in using mirror.