#!/usr/bin/env perl     

use v5.12;
use Data::Dumper;

my %students = (
	x1 => {
		name       => "Alice",
		telephone  => 1001,
		regno      => "x1",
	},
	x2 => {
		name       => "Bob",
		telephone  => 1002,
		regno      => "x2",
	},
	x3 => {
		name       => "Carol",
		telephone  => 1003,
		regno      => "x3",
	},
);

say "Let's look at the data structure...";
print Dumper \%students;

say "What is student x1's telephone number?";
say $students{x1}{telephone};

say "What is Carol's telephone number?";
my ($carol) = grep { $_->{name} eq "Carol" } values %students;
say $carol->{telephone};

say "Now let's delete student x2...";
delete $students{x2};

say "And change Carol's phone number";
$carol->{telephone} = "1004";

say "Let's look at the data structure again...";
print Dumper \%students;