perl map 和grep使用

1.代码为：

my @Array = (1,2,3,4);

my @NewGrep = grep {$_*=2 if($_%2==1);} @Array;
print "@Array \n";
print "@NewGrep \n";
my @NewMap = map {$_*=2 if($_%4==0);$_;} @Array;
print "@Array \n";
print "@NewMap \n";
my @NewMap2 = map {$_*=2,$_,3*$_} @Array;
print "@Array \n";

print "@NewMap2 \n";

  结果为：

C:\Users\bruce\Desktop>perl make2.pl
2 2 6 4
2 6
2 2 6 8
2 2 6 8
4 4 12 16
4 4 12 4 4 12 12 12 36 16 16 48

 2. map 返回多个结果 

#!perl -w
use strict;
my @Number = (1,2,3);
my @MapResult  = map { $_,10+$_,100+$_ } @Number;
print "@MapResult\n";

__END__

结果为：

1 11 101 2 12 102 3 13 103

 

注意

1. $_是数组中的引用，类似foreach中的$_一样；

2. 还有一种用法：

my @Result2 = grep  $_=length($_) ,@HomeName;

    grep EXPR, @Array

    map EXPR, @Array