Perl中的grep和map

grep返回一个数字中符合条件的所有元素；map对数字中所有元素实施转化并返回结果。两者都遍历了数组，但一个用来搜索，一个用来转化。两者都支持表达式或者代码块。

#!/usr/bin/perl -w
use strict;

#get positive number
my @number = (1,2,3,-1,-5);
my @positive_number = grep  $_ > 0,@number;
print "@number: (@number)n";
print "@positive_number: (@positive_number)n";

#get sqrt
my @sqrt_number  = map sqrt $_,@positive_number;
print "@sqrt_number: (@sqrt_number)n";

#split words
my @lines = ( "hello world","not too bad" );
my @words = map m/b(w+)b/g,@lines;
print "@lines size: " . @lines . " (@lines)n";
print "@words size: " . @words . " (@words)n";

#modify email address
my @email_addresses = ( "fei@gmail.com","fei@sina.com.cn" );
my @disguised_addresses = map {
	my $email = $_;
	$email =~ s/@/ at /;
	$email =~ s/./ dot /g;
	$email;
} @email_addresses;
print "@email_addresses: (@email_addresses)n";
print "@disguised_addresses: (@disguised_addresses)n";

参考：http://mailman.linuxchix.org/pipermail/courses/2003-November/001368.html