Try to be more clear - do you actually want to rename an existing file from "file1" to "file1.rtf"? If you do, than perl's 'rename' function should work.

Do

   perldoc -f rename
[download]

at a command prompt to read the perldocs on how to use 'rename' - it's pretty much what you would expect.

Also, you are not using the substitution operator properly - do

   perldoc perlop
[download]

at a command prompt and search (using the forward slash "/") for 'subst' - you'll see all the info you need.

HTH.