while 与 until 控制结构

beyes

until 和 while 是相反的两种用法，后者是条件为真时就一直执行代码块，前者则相反，条件为假时会一直执行代码块并直到条件为真。考虑下面代码：

[Perl] 纯文本查看 复制代码

#!/usr/bin/perl

$i = 10;

while ( $i < 15) {
        print "still running while...$i\n";
        $i++;
}

until ($i < 10) {
        print "still running until...$i\n";
        $i--;
}

运行输出：

# ./until.pl
still running while...10
still running while...11
still running while...12
still running while...13
still running while...14
still running until...15
still running until...14
still running until...13
still running until...12
still running until...11
still running until...10