1 # 2 # The Coffee.pm file to illustrate inheritance. 3 # 4 package Coffee; 5 require Exporter; 6 require Bean; 7 @ISA = qw(Exporter, Bean); 8 @EXPORT = qw(setImports, declareMain, closeMain); 9 # 10 # set item 11 # 12 sub setCoffeeType{ 13 my ($class,$name) = @_; 14 $class->{'Coffee'} = $name; 15 print "Set coffee type to $name n"; 16 } 17 # 18 # constructor 19 # 20 sub new { 21 my $type = shift; 22 my $this = Bean->new(); ##### <- LOOK HERE!!! #### 23 $this->{'Coffee'} = 'Instant'; # unless told otherwise 24 bless $this, $type; 25 return $this; 26 } 27 1; 第6行的require Bean;语句包含了Bean.pm文件和所有相关函数，方法setCoffeeType()用于设置局域变量$class->{'Coffee'}的值。在构造函数new()中，$this指向Bean.pm返回的匿名哈希表的指针，而不是在本地创建一个，下面两个语句分别为创建不同的哈希表从而与Bean.pm构造函数创建的哈希表无关的情况和继承的情况： my $this = {}; #非继承 my $this = $theSuperClass->new(); #继承 下面代码演示如何调用继承的方法：
1 #!/usr/bin/perl 2 push (@INC,'pwd'); 3 use Coffee; 4 $cup = new Coffee; 5 print "n -------------------- Initial values ------------ n"; 6 print "Coffee: $cup->{'Coffee'} n"; 7 print "Bean: $cup->{'Bean'} n"; 8 print "n -------------------- Change Bean Type ---------- n"; 9 $cup->setBeanType('Mixed'); 10 print "Bean Type is now $cup->{'Bean'} n"; 11 print "n ------------------ Change Coffee Type ---------- n"; 12 $cup->setCoffeeType('Instant'); 13 print "Type of coffee: $cup->{'Coffee'} n"; 该代码的结果输出如下：
-------------------- Initial values ------------ Coffee: Instant Bean: Colombian -------------------- Change Bean Type ---------- Set bean to Mixed Bean Type is now Mixed ------------------ Change Coffee Type ---------- Set coffee type to Instant Type of coffee: Instant 上述代码中，先输出对象创建时哈希表中索引为'Bean'和'Coffee'的值，然后调用各成员函数改变值后再输出。 方法可以有多个参数，现在向Coffee.pm模块增加函数makeCup()，代码如下：
sub makeCup { my ($class, $cream, $sugar, $dope) = @_; print "n================================== n"; print "Making a cup n"; print "Add cream n" if ($cream); print "Add $sugar sugar cubesn" if ($sugar); print "Making some really addictive coffee ;-) n" if ($dope); print "================================== n"; } 此函数可有三个参数，不同数目、值的参数产生不同的结果，例如：
1 #!/usr/bin/perl 2 push (@INC,'pwd'); 3 use Coffee; 4 $cup = new Coffee; 5 # 6 # With no parameters 7 # 8 print "n Calling with no parameters: n"; 9 $cup->makeCup; 10 # 11 # With one parameter 12 # 13 print "n Calling with one parameter: n"; 14 $cup->makeCup('1'); 15 # 16 # With two parameters 17 # 18 print "n Calling with two parameters: n"; 19 $cup->makeCup(1,'2'); 20 # 21 # With all three parameters 22 # 23 print "n Calling with three parameters: n"; 24 $cup->makeCup('1',3,'1'); 其结果输出如下：
Calling with no parameters: ================================== Making a cup ================================== Calling with one parameter: ================================== Making a cup Add cream ================================== Calling with two parameters: ================================== Making a cup Add cream Add 2 sugar cubes ================================== Calling with three parameters: ================================== Making a cup Add cream Add 3 sugar cubes Making some really addictive coffee ;-) ================================== 在此例中，函数makeCup()的参数既可为字符串也可为整数，处理结果相同，你也可以把这两种类型的数据处理区分开。在对参数的处理中，可以设置缺省的值，也可以根据实际输入参数值的个数给予不同处理。
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