Do-while in Expect script
#!/usr/bin/expect
set val 0;
set input 5;

do {
    puts "nval = $val"
    set input [expr $input-1];
    set val [expr $val+1];
} while {input}

while true {
    puts "nval = $val"
    incr val
    if {[incr input -1] == 0} break
}