Demonstration of Mojo::Base::tap()

tap.pl

package Cat;
use Mojo::Base -base;

  has name => 'Nyan';
  has ['age', 'weight'] => 4;

package Tiger;
use Mojo::Base 'Cat';

  has friend  => sub { Cat->new };
  has stripes => 42;

package main;
use Mojo::Base -strict;

  my $mew = Cat->new(name => 'Longcat');
  say "\$mew->age = ", $mew->age, " (my age)";
  say "\$mew->age(3)->weight(5)->age = ", $mew->age(3)->weight(5)->age, " (my age, after setting my age and weight)";

  my $rawr = Tiger->new(stripes => 38, weight => 250);
  say '---';
  say "\$rawr->friend->name('Tacgnol1')->weight = ",
    $rawr->friend->name('Tacgnol1') # This returns the object at friend
    ->weight,                       # allowing access to $rawr->friend's methods
    " (my friend's weight)";
  say "\$rawr->tap(sub { \$_->friend->name('Tacgnol2') })->weight = ",
    $rawr->tap(sub { $_->friend->name('Tacgnol2') }) # This returns the object at $rawr
    ->weight,                                        # allowing access to $rawr's methods
    " (my weight, after setting my friend's name)";
  say "\$rawr->friend->name = ", $rawr->friend->name, # Notice the name has been changed, so it's not a temporary change
    " (my friend's name)";

__END__
$mew->age = 4 (my age)
$mew->age(3)->weight(5)->age = 3 (my age, after setting my age and weight)
---
$rawr->friend->name('Tacgnol1')->weight = 4 (my friend's weight)
$rawr->tap(sub { $_->friend->name('Tacgnol2') })->weight = 250 (my weight, after setting my friend's name)
$rawr->friend->name = Tacgnol2 (my friend's name)