expect中为send语句上加变量

#!/usr/bin/expect

set ssh_user "fivetrees"
set password "123456"
spawn ssh -i /root/.ssh/$ssh_user  root@xiaopp.3f.com

expect_before "no)?" {
send "yesr" }
sleep 1

expect "Enter passphrase for key*"
send "$passwordr"

for {set snum 0} {$snum <= 6} {incr snum} {

expect "*#"
send "ls -l /opt/backup/fivetreesdb_s$snumr"

sleep 3
}

sleep 2

expect "*#"
send "echor"

exit