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4d47's solution

to Hello World in the Perl 5 Track

Test suite

The classical introductory exercise. Just say "Hello, World!".

"Hello, World!" is the traditional first program for beginning programming in a new language or environment.

The objectives are simple:

  • Write a function that returns the string "Hello, World!".
  • Run the test suite and make sure that it succeeds.
  • Submit your solution and check it at the website.

If everything goes well, you will be ready to fetch your first real exercise.


This is an exercise to introduce users to using Exercism http://en.wikipedia.org/wiki/%22Hello,_world!%22_program

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


#!/usr/bin/env perl
use strict;
use warnings;
use JSON::PP;
use FindBin;
use lib $FindBin::Bin; # Look for the module inside the same directory as this test file.
use HelloWorld qw(hello);

my $exercise = 'HelloWorld'; # The name of this exercise.
my $test_version = 2; # The version we will be matching against the exercise.
use Test::More tests => 2; # This is how many tests we expect to run.

# If the exercise is updated, we want to make sure other people testing
# your code don't think you've made a mistake if things have changed!
my $exercise_version = $exercise->VERSION // 0;
if ($exercise_version != $test_version) {
  warn "\nExercise version mismatch. Further tests may fail!"
    . "\n$exercise is v$exercise_version. "
    . "Test is v$test_version.\n";

can_ok $exercise, 'import' or BAIL_OUT 'Cannot import subroutines from module';

my $C_DATA = do { local $/; decode_json(<DATA>); };
is hello($_->{input}), $_->{expected}, $_->{description} foreach @{$C_DATA->{cases}};

  "exercise": "hello-world",
  "version": "1.1.0",
  "cases": [
      "description": "Say Hi!",
      "property": "hello",
      "input": {},
      "expected": "Hello, World!"
package HelloWorld 2;

use strict;
use warnings;
use Exporter 'import';
our @EXPORT_OK = qw(hello);

sub hello {
  'Hello, World!'


What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?