BEGIN {
    open OLDERR, '>&STDERR' 
        or die "Couldn't dupe STDERR.\n$!";;
    open STDERR, '>>', 'errors.log' 
        or die "Couldn't redirect STDERR.\n$!";
    print STDERR 'Starting run of $0 at ', 
                 scalar localtime, 
                 ", with parameters: @ARGV\n";
}