perl 0.11 引用

ref(XXX)  判断一个引用是什么数据结构 
#变量引用
```perl
my $var=1;
my $ref=\$var;
print ref($ref)."\n";
print "$ref\n";
print ${$ref}."\n";
[root@test ~]# ./a.pl
SCALAR                               #标量
SCALAR(0x19adba0)                    #标量和地址
1
```
***
#数组引用
##创建数组的引用
```perl
my @array1 = qw { aaa bbb ccc };
my @array2 = qw { 111 222 };
push @array2 , \@array1;
my $ref= \@array2;
print 'ref($ref)='.ref($ref)."\n";
print '${$ref}[0]='.${$ref}[0]."\n";
print '$ref->[1]='.$ref->[1]."\n";
print '$ref->[2][1]='.$ref->[2][1]."\n";
$ref->[2][1]="changed succeed";
print '$array1[1]='.$array1[1]."\n";
[root@test ~]# ./a.pl
ref($ref)=ARRAY
${$ref}[0]=111
$ref->[1]=222
$ref->[2][1]=bbb
$array1[1]=changed succeed
```
##直接用引用创建数组
```perl
my $ref;
$ref->[0] = "1";
$ref->[1]->[0] = "21";
$ref->[1]->[1] = "22";
$ref->[2] = "3";
print '@{$ref}[0]='.@{$ref}[0]."\n";
print '$ref->[1]->[0]='.$ref->[1]->[0]."\n";
[root@test ~]# ./b.pl
@{$ref}[0]=1
$ref->[1]->[0]=21
```
***
#hash引用
##创建hash的引用
```perl
my %hash1 = ( "first" => "aaa", "second" => "bbb", "third" => "ccc" );
my %hash2 = ( "2first" => "11", "2second" => \%hash1, "2third" => "22" );
my $ref = \%hash2;
print 'ref($ref)='.ref($ref)."\n";
print '${$ref}{"2first"}='.${$ref}{"2first"}."\n";
print '$ref->{"2second"}->{"first"}='.$ref->{"2second"}->{"first"}."\n";
$ref->{"2second"}->{"third"} = "changed succeed";
print '$hash1{"third"}='.$hash1{"third"}."\n";
[root@test ~]# ./a.pl
ref($ref)=HASH
${$ref}{"2first"}=11
$ref->{"2second"}->{"first"}=aaa
$hash1{"third"}=changed succeed
```
##直接用引用创建hash
```perl
my $ref;
$ref->{"first"} = 1;
$ref->{"second"}->{"first"} = 21;
$ref->{"second"}->{"second"} = 22;
$ref->{"third"} = 3;
print Dumper %{$ref};
print $ref->{"second"}->{"second"}."\n";
```
***
#符号引用
**不能用my  不能用use strict, 不建议使用**
```perl
$str="var";
$var="it is me";
print $$str."\n";  # 理解成$( $str ) => $( var ) => $var => "it is me"    很妖的写法
[root@test ~]# ./a.pl
it is me
```

乱读天书， 不求甚解

乱读天书，不求甚解