The var argument is the name of a Tcl variable that will contain the loop index. The loop index is set to the value specified by first. The Tcl interpreter is invoked upon body zero or more times, where var is incremented by increment every time through the loop, or by one if increment is not specified. increment can be negative in which case the loop will count downwards.
When var reaches limit, the loop terminates without a subsequent execution of body. For instance, if the original loop parameters would cause loop to terminate, say first was one, limit was zero and increment was not specified or was non-negative, body is not executed at all and loop returns.
first, limit and increment are integer expressions. They are only evaluated once at the beginning of the loop.
If a continue command is invoked within body then any remaining commands in the current execution of body are skipped, as in the for command. If a break command is invoked within body then the loop command will return immediately.
loop returns an empty string.