- Open the output file.
- Use binmode on the output file handle.
- For each input file to concatenate,
   - Open the next input file.
   - Use binmode on the input file handle.
   - While you haven't reached the end of the input file,
     - Read from the input file handle
     - Write what you read
   }
}

##</code><code>##

{
   # This code must be provided $output and $ext.

   local $/ = \4096;  # Limit the size of our block.

   local *OUT;
   open(OUT, "> $output")
   or die("Can't create output file: $!");
   binmode(OUT);

   local $_;
   while (glob("*.$ext")) {
      local *IN;
      open(IN, "< $_")
      or die("Can't open input file $_: $!");
      binmode(IN);

      {
         local $_;
         print OUT $_ while <IN>;
      }
   }
}

##</code><code>##

copy /b *.ext output

##</code><code>##

cat *.ext > output