use warnings;
use strict;

open(my $out, ">", shift(@ARGV) ) or die $!;
my $buffer_length = 16_384;
while( my $file = shift(@ARGV) ) {
   open(my $fh, $file) or die $!;
   while( read($fh, my $buffer, $buffer_length) ) {
      print $out $buffer or die $!;
   }
   close $fh;
}
close $out or die $!;