问一下perl的变量的作用域问题

jacksting

程序如下：
#!/usr/bin/perl -w

print "Enter three numbers: ";
chomp($nums = <STDIN>);

($num1, $num2, $num3) = split(" ", $nums);

print "In MAIN: ", $num1, " ", $num2, " ", $num3, "\n";
proc1($num1, $num2, $num3);
print "In MAIN: ", $num1, " ", $num2, " ", $num3, "\n";

sub proc1  {
    my $num2 = 100;
    local $num3 = 200;
    ($num1, $num2, $num3) = @_;
    ($num1, $num2, $num3) = ($num1+2, $num2+2, $num3+2);
    print "In PROC1: ", $num1, " ", $num2, " ", $num3, "\n";
    proc2();
    print "In PROC1: ", $num1, " ", $num2, " ", $num3, "\n";
}

sub proc2 {
    $num1++;   # Global $num1
    $num2++;   # Global $num2
    $num3++;   # $num3 from proc1
    print "In PROC2: ", $num1, " ", $num2, " ", $num3, "\n";
}

###############
运行结果：
[root@localhost perlstd]# perl sub_call.pl
Enter three numbers: 1 1 1
In MAIN:   1 1 1
In PROC1: 3 3 3
In PROC2: 4 2 4
In PROC1: 4 3 4
In MAIN:    4 2 1
为什么$num2的表现跟我感觉的常识不一样呢？到底本地作用域和全局以及动态作用域是怎么覆盖的？

flw

晕～
测语法也不用这么测吧？
还加来减去的，我都晕了。

BTW:
use strict;
use warnings;
一下，对你有好处。

xiaoshengcaicai

程序的输出应该是正确的

楼主可能是对my跟local的区别不是很理解：

楼主可以试试揣摩一下下面的代码：

#!/usr/bin/perl
use strict;
our $num2 = 1;

proc1();
print "MAIN: $num2\n";

sub proc1 {
    my $num2 = 2;
    proc2();
    print "PROC1: $num2\n";
}

sub proc2 {
     print "PROC2: $num2\n";
     $num2 = 3;
}

输出

PROC2: 1
PROC1: 2
MAIN: 3

另外一段代码

#!/usr/bin/perl
use strict;
our $num2 = 1;

proc1();
print "MAIN: $num2\n";

sub proc1 {
    local $num2 = 2;
    proc2();
    print "PROC1: $num2\n";
}

sub proc2 {
     print "PROC2: $num2\n";
     $num2 = 3;
}

输出

PROC2: 2
PROC1: 3
MAIN: 1

[ 本帖最后由 xiaoshengcaicai 于 2006-12-28 12:17 编辑 ]

福瑞哈哥

3楼贴的两段代码使我明白了my和local,赞一个。

jacksting

呵呵，谢谢楼上的，分开看就清楚了。