new files

Task/Delegates/Perl/delegates-1.pl

@@ -0,0 +1,38 @@
+use strict;
+
+package Delegator;
+sub new {
+   bless {}
+}
+sub operation {
+   my ($self) = @_;
+   if (defined $self->{delegate} && $self->{delegate}->can('thing')) {
+      $self->{delegate}->thing;
+   } else {
+      'default implementation';
+   }
+}
+1;
+
+package Delegate;
+sub new {
+   bless {};
+}
+sub thing {
+   'delegate implementation'
+}
+1;
+
+
+package main;
+# No delegate
+my $a = Delegator->new;
+$a->operation eq 'default implementation' or die;
+
+# With a delegate that does not implement "thing"
+$a->{delegate} = 'A delegate may be any object';
+$a->operation eq 'default implementation' or die;
+
+# With delegate that implements "thing"
+$a->{delegate} = Delegate->new;
+$a->operation eq 'delegate implementation' or die;