perl 中的my和全局变量

$Some::stuff 使用包some的标准变量$stuff


our 把名字限制于一个作用域,

local 把值限制于一个作用域,

my 把名字和值都限制于一个作用域



my变量:
[root@master Webqq]# cat t5.pl 
{my $var=11;print "$var is 1--$var
";}{print "$var is 2--$var
"};
{our $var=11;print "$var is 1--$var
";}{print "$var is 2--$var
"};
[root@master Webqq]# perl t5.pl 
$var is 1--11
$var is 2--
$var is 1--11
$var is 2--11



our变量:

[root@master Webqq]# cat t6.pl 
our $PROGRAM_NAME = "waiter";
{
my $PROGRAM_NAME = "something";
print "$PROGRAM_NAME is 1---$PROGRAM_NAME
";
our $PROGRAM_NAME = "server"; #这里的our和外面的相同，和前句不同。
print "$PROGRAM_NAME is 2----$PROGRAM_NAME
";
# 这里调用的代码看到的是"server"
 }
print "$PROGRAM_NAME is 3----$PROGRAM_NAME
";
[root@master Webqq]# perl t6.pl 
$PROGRAM_NAME is 1---something
$PROGRAM_NAME is 2----server
$PROGRAM_NAME is 3----server
[root@master Webqq]# 


my 声明的是词法变量，"把名字和值都限于限于某个范围",简单说，就是只能本层模块或者函数可以看到这个变量，高一层的或

者低一层的都看不到的。例如：
sub greeting1{
my ($hello) = "How are you do?";
greeting2();
}
sub greeting2{
print "$hello/n";
}
$hello = "How are you doing?";
greeting2();
greeting1();
greeting2();
运行结果：
How are you doing?
How are you doing?
How are you doing?
一个 How are you do? 都没有,在greeting1中call greeting2时，greeting2看不到greeting1的私有 $hello变量，只能看到外

面的全局变量$hello