Scripting Backup to FTP

I am creating a script to backup and ftp, would when creating the backup file was inserted the name of the system for better identification, eg:

/ip routes export file=$GlobalVariable

But when running the script is not generating the file, I think it is a problem in assigning the name to be a variable, does anyone have any idea how to accomplish the task is?

/ip route export file=$GlobalVariable

use this…

/export file=“$[/system identity get name]”