no warnings;
use File::Map ':all';

open(my $fh, '+>>', shift) or die; # open/mmap modes must ~~
my $off = $fh->tell;
print $fh join " ", @ARGV;
$fh->flush;

# rotate in place
map_handle(my $mmap, $fh, '+<');
substr($mmap, 0, 0, substr($mmap, $off));

##</code><code>##

no strict;
no warnings;
use File::Map ':all';

my $fnam = shift @ARGV or die;
open(my $fh, '>>', $fnam) or die;
my $off = -s $fh;

print $fh join " ", @ARGV;
close $fh; # !

# rotate in place
map_file my $mmap, $fnam, '+<';
substr($mmap, 0, 0, substr($mmap, $off));