FWIW: On my single-disk, Windows system, this is almost twice as fast as File::Copy.

Here, using a 10 MB buffer seems to strike the right balance between latency and head shuffling; but if you are on a multi-disk system that balance point may be considerably different.

#! perl -slw
use strict;

our $BUFSIZE //= 10*1024**2;

my( $source, $target ) = @ARGV;

open IN, '<', $source or die "$source: $!";
binmode IN;
open OUT, '>>', $target or die "$target: $!";
binmode OUT;

{
    local( $/, $\ ) = \$BUFSIZE;
    print OUT while <IN>;
}

close OUT;
close IN;
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