perl中子程序中参数的两种引用(传递)方式介绍

use strict;
#这里是两个数组
my @i =('1','2','3');
my @j =('a','b','c');

#在进行处理之前，我们把他们先打印出来，看一看他们的样子
print "In main program before calling subroutine:i="."@i\n";
print "In main program before calling subroutine:j="."@j\n";

#然后我们通过子程序进行处理
reference_sub(@i,@j);
print "In main program after calling subroutine:i="."@i\n";
print "In main program after calling subroutine:j="."@j\n";
#下面是子程序
sub reference_sub
{
 my (@i,@j)=@_;
 print "In subroutine:i="."@i\n";
 print "in subroutine:j="."@j\n";

 #这里我们对@_的处理用pop,和shift来进行
 push(@i,'4');
 shift(@j);
}

F:\&;perl\a.pl
In main program before calling subroutine:i=1 2 3
In main program before calling subroutine:j=a b c
In subroutine:i=1 2 3 a b c
in subroutine:j=
In main program after calling subroutine:i=1 2 3
In main program after calling subroutine:j=a b c
F:\&;

use strict;

#这里是两个数组
my @i =('1','2','3');
my @j =('a','b','c');

#在进行处理之前，我们把他们先打印出来，看一看他们的样子
print "In main program before calling subroutine:i="."@i\n";
print "In main program before calling subroutine:j="."@j\n";

#然后我们通过子程序进行处理
reference_sub(\@i,\@j);#在这里我们添加了反斜线，也就是pass byreference（传入引用，在大骆驼书中第六章翻译）
print "In main program after calling subroutine:i="."@i\n";
print "In main program after calling subroutine:j="."@j\n";
#下面是子程序
sub reference_sub
{
 my ($i,$j)=@_;#引用也是一种特殊的数据形式，它们在@_中都被当成标量变量来储存
 print "In subroutine:i="."@$i\n";所以这里引用它们的时候，我们在他们前面添加了两个符号，@代表这是一个数组，$代表着是一个二次引用。
 print "in subroutine:j="."@$j\n";
    print "In subroutine:the third element is $$j[2]\n";#当引用数组中的一个元素的时候第一个$和后面的j[2]代表数组中的第三个元素，而第二个$代表的就是二次引用
 #这里我们对@_的处理用pop,和shift来进行
 push(@$i,'4');
 shift(@$j);
}

F:\&;perl\a.pl
In main program before calling subroutine:i=1 2 3
In main program before calling subroutine:j=a b c
In subroutine:i=1 2 3
in subroutine:j=a b c
In subroutine:the third element is c
In main program after calling subroutine:i=1 2 3 4
In main program after calling subroutine:j=b c
F:\&;