my %channel_map;
for my $channel ( keys %files_by_channel )
{
    $channel_map{$_} = $channel for keys %{ $files_by_channel{$channel} };
}

printf "%-10s %-15s %-40s\n", 'File#',  'Channel Name', 'File Name';
printf "%-10s %-15s %-40s\n", '-' x 10, '-' x 15,       '-' x 40;

for my $file_number ( sort keys %files_by_number )
{
    printf "%-10s %-15s %-40s\n",
             $file_number,
             $channel_map{$file_number},
             $files_by_number{$file_number};
}