代码：
use
strict;
use
warnings;
my
$test
=
"
asdf
"
;
print
"
${test}_test2\n
"
;
#
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
"
$a1\n
"
;
my
$a2
=
undef
;
print
"
$a2\n
"
;
if
(!
defined
(
$a1
)){
print
"
a1 is not defined\n
"
;}
if
(!
$a2
){
print
"
a2 is not defined\n
"
;}
my
$a3
=
''
;
if
(!
$a3
){
print
"
a3 is empty string\n
"
;}
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！
作者：
iTech
微信公众号: cicdops
出处：
http://itech.cnblogs.com/
github：
https://github.com/cicdops/cicdops
