       1mloop 4m22mvar24m 4mfirst24m 4mlimit24m 4m?increment?24m 4mbody0m
              1mLoop  22mis  a  looping command, similar in behavior to the Tcl 1mfor0m
              statement, except that the 1mloop 22mstatement achieves substantially
              higher  performance and is easier to code when the beginning and
              ending values of a loop are known, and the loop variable  is  to
              be  incremented  by a known, fixed amount every time through the
              loop.

               The 4mvar24m argument is the name of a Tcl variable that  will  con-
              tain  the loop index.  The loop index is set to the value speci-
              fied by 4mfirst24m.  The Tcl interpreter is invoked upon 4mbody24m zero or
              more  times,  where  4mvar24m  is incremented by 4mincrement24m every time
              through the loop, or by  one  if  4mincrement24m  is  not  specified.
              4mIncrement24m  can  be  negative  in  which case the loop will count
              downwards.

              When 4mvar24m reaches 4mlimit24m, the loop terminates without a subsequent
              execution  of  4mbody24m.  For instance, if the original 1mloop 22mparame-
              ters would cause 1mloop 22mto terminate, say 4mfirst24m was one, 4mlimit24m was
              zero  and  4mincrement24m was not specified or was non-negative, 4mbody0m
              is not executed at all and 1mloop 22mreturns.

              The 4mfirst24m, 4mlimit24m and 4mincrement24m are  integer  expressions.   They
              are only evaluated once at the beginning of the loop.

              If  a 1mcontinue 22mcommand is invoked within 4mbody24m then any remaining
              commands in the current execution of 4mbody24m are skipped, as in the
              1mfor 22mcommand.  If a 1mbreak 22mcommand is invoked within 4mbody24m then the
              1mloop 22mcommand will return immediately.   1mLoop  22mreturns  an  empty
              string.
