1. 利用POSIX模块处理向下/向上取整

use POSIX;
 
POSIX::ceil(3.14) => 4   #向上取整
 
POSIX::floor(3.14) => 3   # 向下取整， 等同于 int(3.14)

2. 利用Math::Round 做四舍五入

use Math::Round;
 
my $num = 45.4;
 
my $round = Math::Round($num);