AIX

while [ $x ] ; do
     while [ $y ] ; do
          while [ $z ] ; do
               break 2
          done
     done
     # the "break 2" will bring you here
done

typeset -i continuation=1

while [ $continuation -gt 0 ] ; do
     print "enter a value: " ; read input
     case $input in
          a)
               # do somenthing
               ;;
 
          b)
               # do something else
               ;;

          z)
               continuation=0     # exit loop
               ;;
 
          *) 
               print "don't enter garbage svp"
               ;;
 
     esac
done