while loop
until
while

    The loop construct, found in nearly all
   procedural languages, that executes one or more instructions
   (the "loop body") repeatedly so long as some condition
   evaluates to true.  In contrast to a repeat loop, the loop
   body will not be executed at all if the condition is false on
   entry to the while.

   For example, in C, a while loop is written

   	while () ;

   where  is any expression and  is any
   statement, including a compound statement within braces
   "..".

   A for loop, e.g. in the C language, extends the while loop
   syntax to collect pre-loop initialisation and loop-end logic
   into the beginning of the statement.

   Perl provides the "until" loop that loops until the loop
   condition is true.

   (2009-10-07)