merge 2 or more files together without creating new file

Hi,
Is there a way I can marge FILE2 into FILE1 or reverse together
without creating a new merge file. I am not sure there are a better
way to do it. If you give me some hint or help, i would appreciate
it.
thx.
Here is my code.

#!/bin/usr/perl

open(FILE1, /usr/test1.txt);
@temp =<FILE1>;
close (FILE1);

open(FILE2, /usr/test2.txt);
@temp =<FILE2>;
close (FILE2);

.