如果观察者也是主体，如何应用观察者模式(How to apply observer pattern if observers are also subjects)

 我正在试图恢复一个不足的模块（Zoidberg），你可以做的最好的方法是挖掘CPANtesters的结果，以查看出错的地方，以便尝试修复它。 
 
 这就是说谷歌地图有一个公共的API，甚至一个简单的Web界面 。 我会试着嘲笑你一个例子，但为了让自己开始尝试用LWP::UserAgent或WWW::Mechanize做一些请求，然后解析出结果以找到你的答案。 
 
 编辑：好的，这是一个例子。 接近结尾$data是上面链接中描述的JSON响应中包含的数据的hashref。 我也计算了（第一）路线的总距离。 
 
#!/usr/bin/perl

use strict;
use warnings;

use JSON;

use LWP::UserAgent;
my $ua = LWP::UserAgent->new();

my $origin = "60607";
my $destination = "60067";

my $site = 'http://maps.googleapis.com/maps/api/directions/';
my $mode = 'json';

my $page = $site . $mode . '?origin="' . $origin . '"&destination="' . $destination . '"&sensor=false';

my $response = $ua->get( $page );
my $json = $response->content();

my $data = decode_json $json;

my @legs = @{ $data->{'routes'}[0]{'legs'} };
my $distance_meters = 0;
foreach my $leg (@legs) {
    $distance_meters += $leg->{'distance'}{'value'};
}

my $distance_kilometers = $distance_meters / 1000;
my $distance_miles = $distance_kilometers * 0.62137119;
print $distance_miles . " Miles\n";
 
 编辑：现在，因为我在周日下午感到无聊： 
 
perl -e 'use JSON;use LWP::Simple;($s,$e)=@ARGV;$m+=$_->{distance}{value}for@{(decode_json get qq<http://maps.googleapis.com/maps/api/directions/json?origin="$s"&destination="$e"&sensor=false>)->{routes}[0]{legs}};printf"%.2f Miles\n",$m*0.6213e-3' 60607 60067
 
 编辑：现在， Mojolicious系统的一个端口： 
 
perl -Mojo -E '$m+=$_->{distance}{value}for@{g("http://maps.googleapis.com/maps/api/directions/json",form=>{origin=>shift,destination=>shift,sensor=>"false"})->json("/routes/0/legs")};printf"%.2f Miles\n",$m*0.6213e-3' 60607 60067

I am in the process of trying to recover an undermaintained module (Zoidberg) and the best you can do is dig through the results of the CPANtesters to see what went wrong in order to try to fix it.
 
That said google maps has a public api and even one with a simple web interface. I will try to mock you up an example, but to get yourself started try doing some requests with LWP::UserAgent or WWW::Mechanize and then parse out the results to find your answer.
 
Edit: Ok here is an example. Near the end $data is a hashref of the data contained in the JSON response described in the link above. I have also calculated the total distance for the (first) route.
 
#!/usr/bin/perl

use strict;
use warnings;

use JSON;

use LWP::UserAgent;
my $ua = LWP::UserAgent->new();

my $origin = "60607";
my $destination = "60067";

my $site = 'http://maps.googleapis.com/maps/api/directions/';
my $mode = 'json';

my $page = $site . $mode . '?origin="' . $origin . '"&destination="' . $destination . '"&sensor=false';

my $response = $ua->get( $page );
my $json = $response->content();

my $data = decode_json $json;

my @legs = @{ $data->{'routes'}[0]{'legs'} };
my $distance_meters = 0;
foreach my $leg (@legs) {
    $distance_meters += $leg->{'distance'}{'value'};
}

my $distance_kilometers = $distance_meters / 1000;
my $distance_miles = $distance_kilometers * 0.62137119;
print $distance_miles . " Miles\n";
 
Edit: And now, since I was bored on a Sunday afternoon:
 
perl -e 'use JSON;use LWP::Simple;($s,$e)=@ARGV;$m+=$_->{distance}{value}for@{(decode_json get qq<http://maps.googleapis.com/maps/api/directions/json?origin="$s"&destination="$e"&sensor=false>)->{routes}[0]{legs}};printf"%.2f Miles\n",$m*0.6213e-3' 60607 60067
 
Edit: And now, a port of the one liner to the Mojolicious system:
 
perl -Mojo -E '$m+=$_->{distance}{value}for@{g("http://maps.googleapis.com/maps/api/directions/json",form=>{origin=>shift,destination=>shift,sensor=>"false"})->json("/routes/0/legs")};printf"%.2f Miles\n",$m*0.6213e-3' 60607 60067