While() — Starts a while
loop
Starts a while loop.
Execution will return to this point when EndWhile() is called, until
expr is no longer true. If a condition is met
causing the loop to exit, Asterisk continues execution of the dialplan
on the next priority after the corresponding EndWhile().
exten => 123,1,Set(COUNT=1)
exten => 123,2,While($[ ${COUNT} < 5 ])
exten => 123,3,SayNumber(${COUNT})
exten => 123,4,Set(COUNT=$[${COUNT} + 1])
exten => 123,5,EndWhile()