perl的一些函数（二）
1. tr 转换 转换不是替换（tr///==y///）tr/searchlist/replacementlist/用于查找某个一个字符串，并用replacementlist替换，可以使用正则表达式
my $str="this Is A teST";
$str=~tr/a-z/A-Z/; 把小写转换为大写 会输出THIS IS A TEST
s///options
g 全局替换
i 忽略大小写
my $str3="this is a test\n";
$str3=~s/t/haha/g; =====>hahahis is a hahaeshaha
print $str3;
$str3=~s/HaHa/t/ig; =====>this is a test
print $str3;
this is a test
tr 与 替换的区别
tr可以使用正则表达式，替换不行，没法使用$str=~s/a-z/A-Z/; 不会有任何改变 tr/ab/ABC/ 替换原则是a->A b->B 而s/ab/ABC/会将ab->ABC
[*]tr/// The transliteration operator. Same as y///.
$count= $str3=~ tr/i/i/; # count the stars in $sky countthe number of a and store into $count
统计i的个数存放在$count
#!/usr/bin/perl
use strict;
my $str1="this Is A tr TEST";
my $str2="this Is A tr TEST";
$str1=~s/t/T/g;
$str2=~tr/a-z/A-Z/;
print "$str1\n";
print "$str2\n";
my $str3="this is a test\n";
my $count=$str3=~tr/i/i/;
print "\ncount the number of i --->$count<----\n";
结果：
D:\>perl tr.pl
This Is A Tr TEST
THIS IS A TR TEST
count the number of i --->2<----
trOptions:
c Complement the SEARCHLIST. 清单没写到的就补给他右边清单的最后一个字元
d Delete found but unreplaced characters. 对照表中没有的项目就删掉
s Squash duplicate replaced characters. 重复的字符变成一个
my $strs="have a good day\n";
$strs=~tr/a/_/c; =====>_a___a_______a__
print $strs;
my $strs="have a good day\n";
$strs=~tr/ao/Ao/s; =====>hAve A god dAy 两个O变成一个
my $strs="have a good day\n";
$strs=~tr/hag/HA/d; ===>HAve A ood dAy
参考：http://www.cnblogs.com/blueicely/archive/2012/12/13/2816371.html
生成随机数：
rand
Returns a random fractional number greater than or equal to 0 and less than the value of EXPR.
example：
int(rand(10))
returns a random integer between 0 and 9, inclusive.
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