cycle

set l [list a bc def 1 23 456]
set m 0

foreach i $l {
    incr m
    puts "member $m is $i"
}

for {set x 0} {$x<10} {incr x} {
   puts "x is $x"
}

set x 0
while {$x<10} {
    puts "x is $x"
    incr x
}

This command is typically invoked inside the body of a looping command such as for or foreach or while.
for {set x 0} {$x<10} {incr x} {
   if {$x > 5} {
      break
   }
   puts "x is $x"
}