References examples and syntax

05 critter.pl

use strict;
use warnings;
use v5.14;
use Critter;

my $c = Critter->new('joe', 19);
my $d = Critter->new('bob', 100);
my $e = Critter->new('jane', 12);

$c->eat();
$c->eat();

$d->eat();

05 Critter.pm

# Critter.pm
#
package Critter;
use strict;
use warnings;
use v5.14;

sub new {
  my ( $cls, $name, $age ) = @_;

  my $self = {
    name => $name,
    age => $age,
  };

  bless $self, $cls;
}


sub eat {
  my ( $self ) = @_;
  my $name = $self->{name};

  say "$name: Yummy...";
}



1;

plants.pl

use strict;
use warnings;
use v5.16;

# Notice we import the hit_aliens subroutine
# from Plants package
use Plants qw/hit_aliens/;
use Aliens;

# So now we can call it directly
hit_aliens();

# Or using the full name
Plants::hit_aliens();

Plants.pm

# Plants.pm
# Plants module example
package Plants;

use strict;
use warnings;
use v5.16;
use base 'Exporter';

our @EXPORT_OK = qw/hit_aliens/;

sub secret_weapon { "plants win" }

sub hit_aliens { say secret_weapon() }

1;

refs.pl

use strict;
use warnings;
use v5.12;

my @l = (1, 2, 5, 9, 19);
my $l_ref = \@l;

say "list = ", @$l_ref;

push @$l_ref, 7;

my %h = (
  bob => 'bob@gmail.com',
  tim => 'tim@yahoo.com',
);

my $h_ref = \%h;

say $h_ref->{bob};

my $sz = scalar keys %$h_ref;

sub hello { say "hello" }

my $hello_ref = \&hello;

$hello_ref->();
$hello_ref->(7);
################################

my $g_ref = [1, 2, 7];

my @game = (
   [ ' ', 'x', 'o' ],
   [ ' ', 'o', 'x' ],
   [ ' ', 'x', 'x' ],
);

$game[2]->[0] = 'x';

# same as ...
$game[2][0] = 'x';

refs2.pl

use strict;
use warnings;
use v5.16;
use Test::More;
###########################################

my @contacts = (
  { name => 'joe', email => 'joe@gmail.com', city => 'Haifa' },
  { name => 'bob', email => 'bob@gmail.com', city => 'Yakum' },
  { name => 'mike', email => 'mike@yahoo.com', city => 'Jerusalem' },
  { name => 'jane', email => 'jane@walla.com', city => 'Haifa' },
);

my @gmail = grep { $_->{email} =~ /gmail.com/ } @contacts;
grep { $_->{city} eq 'Haifa' } @contacts;

is_deeply(
  \@gmail,
  [ { name => 'joe', email => 'joe@gmail.com', city => 'Haifa' },
    { name => 'bob', email => 'bob@gmail.com', city => 'Yakum' },
  ]);

###########################################

sub sum {
  my $sum = 0;
  $sum += $_ for @_;

  $sum;
}


sub diffsum {
  my ( $l1_ref, $l2_ref ) = @_;
  my @l1 = @$l1_ref;
  my @l2 = @$l2_ref;

  sum(@l1) - sum(@l2)
}

my @data = (
  [ [10, 8, 2], [ 10, 8, 1 ], 1 ],
  [ [11, 2],    [10 ],        3 ],
  [ [1, 2, 3],  [],           6 ],
);

for my $t_ref (@data) {
  is( diffsum($t_ref->[0], $t_ref->[1]), $t_ref->[2] );
}

sub add_to_hash {
  my ( $h_ref, $k, $v ) = @_;

  $h_ref->{$k} = $v;
}

my %data = ( a => 1, b => 2 );

add_to_hash(\%data, c => 3);

is( $data{c}, 3, "Item 3 added to hash");

done_testing;