#!perl
my $blocksize = (stat'.')[11] || 4096;

open ( my $s, "<", "source" ) or die "Could not open source file: $!\n";
open ( my $d , ">>", "dest" ) or die "Could not open destination file : $!\n";

my $buffer;

do {
    local $/ = \$blocksize;
    print {$d} $buffer while ( $buffer = <$s> );
}