perl常量+多维数组+变量的初始化

发布时间：2020-12-16 00:16:22 所属栏目：大数据来源：网络整理

导读：代码： ? use ?strict; ? use ?warnings; my ? $test ?=? " asdf " ; print ? " ${test}_test2n " ; # constant use ?constant?{ ????AAA?=? " aaa " , ????BBB=? " bbb " , ????MIN_TOTAL?=? 12 , ????SCORE_PASS?=? 90 , ????SCORE_RED?=? 70 , }; print

代码：

use ?strict;?
use?warnings;

my? $test?=? " asdf ";
print? " ${test}_test2n ";

# constant
use?constant?{
????AAA?=>? " aaa ",
????BBB=>? " bbb ",
????MIN_TOTAL?=>? 12,
????SCORE_PASS?=>? 90,
????SCORE_RED?=>? 70,
};

print?AAA;
print?SCORE_PASS;

# two?dimesion?arrays
my? @steps?=?(
??????[ " aaa ",? " aaavalue "],
??????[ " bbb "," bbbvalue "],
??????[ " ccc "," cccvalue "]
);
print? " n ";
foreach? my? $i?( 0?..?$ # steps){
?? print? " $steps[$i][0]:$steps[$i][1]n ";
}

代码2：

my? $a1;
print? " $a1n ";
my? $a2?=? undef;
print? " $a2n ";
if(! defined( $a1)){ print? " a1?is?not?definedn ";}
if(! $a2){ print? " a2?is?not?definedn ";}
my? $a3= '';
if (! $a3 ){ print? " a3?is?empty?stringn ;}??

在定义变量时一定要初始化，或者在使用时判断是否defined，很多的时候还需要判断是否为空字符串。特别是在使用getopt::long或cgi->query获得参数后要检测是否定义，如果么有定义考虑给予默认值。

完！?

（编辑：李大同）

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