perl笔记 hash

#!perl -w
use strict;
my %hash_test_weekday=("Mon","星期一","Wed","星期二");
print $hash_test_weekday{"Mon"},"\n";
$hash_test_weekday{"Sun"}="星期日";
&println(%hash_test_weekday);
print %hash_test_weekday,"\n";
print "%hash_test_weekday\n";
#哈希翻转。（赋值的时候先转成列表，所以翻转后原来哈系的值和键翻转了
my %hash_test_weekday_r=reverse %hash_test_weekday;
print %hash_test_weekday_r,"\n";
#使用胖箭头为哈希赋值 ######在后面添加一个额外的逗号是个好习惯
%hash_test_weekday=("Sat"=>"星期六"=>    # "=>"胖箭头就等于逗号。但是为了引人胖箭头就是为了容易阅读
Tus=>"星期几",);     #胖箭头的左侧可以使用裸词。裸词：字母数字下划线的序列，可用加减号开头，不能用数字开头
print %hash_test_weekday,"\n"; 
#keys和values函数
&println("--------keys和values函数------------");
my @keys_weekday=keys %hash_test_weekday;
my @values_weekday=values %hash_test_weekday;
print "@keys_weekday","\n";
print "@values_weekday","\n";

#each函数
&println("--------each函数------------");
while(my ($key,$value)=each %hash_test_weekday){
print "$key=>$value\n"
}

#exists函数
&println("--------exists函数------------");
if(exists $hash_test_weekday{"Sat"}){
print "there's a key named Sat, its value is $hash_test_weekday{Sat}\n";
}
#delete函数
&println("--------delete函数------------");
delete $hash_test_weekday{Sat};
print %hash_test_weekday,"\n";

&list_hash_entry(\%hash_test_weekday);  #"\"必须加
&list_env_items;
sub println{
print "@_"."\n"
}
sub list_hash_entry{#接收哈希参数
my($hash)=@_;
foreach my $key (sort keys %$hash){
if($key){print "$key","--------","$hash->{$key}\n";}
}
}
sub list_env_items{
my $longest=0;
foreach (keys %ENV){
my $key_length=length($_);
$longest=$key_length if $key_length>$longest;
}
foreach (sort keys %ENV){
printf "%-${longest}s = %s \n",$_,$ENV{$_};
}
}