sub note_to_sound {
    my ($note) = @_;
    
    return $notes{$note};
}

use Test::More tests => 8;

return 1 if caller();  # Done if loaded as a module

my $song = make_SoM_song (join ' ', 'a' .. 'g');
my @expected = map{note_to_sound($_)} 'a' .. 'g';

Test::More::is_deeply($song, \@expected, "Notes map correctly to phrases");

my %noteCounts;
my $samples = 100000;
my $nominal = $samples / 7;

++$noteCounts{random_SoM_note($_)} for 1 .. $samples;

Test::More::ok (abs($noteCounts{$_} - $nominal) < 200, "Random distribution of $_: $noteCounts{$_}")
    for map {note_to_sound($_)} 'a' .. 'g';

##</code><code>##

package SoundOfMusicSong;
use strict;
use warnings;

my %SoM = (
    'c' => {phrase => 'a deer a female deer',       sound => 'do'},
    'd' => {phrase => 'a drop of golden sun',       sound => 're'},
    'e' => {phrase => 'a name I call myself',       sound => 'me'},
    'f' => {phrase => 'a long long way to run',     sound => 'fa'},
    'g' => {phrase => 'a needle pulling thread',    sound => 'so'},
    'a' => {phrase => 'a note to follow so',        sound => 'la'},
    'b' => {phrase => 'a drink with jam and bread', sound => 'te'},
    );
my @notes = keys %SoM;

sub make_SoM_song {
    my ($user_song) = @_;

    return [
        map {exists $SoM{$_} ? $SoM{$_}->{sound} : 'not a note'}
        split /\W+/, $user_song
        ];
}

sub getPhrase {
    my ($user_song) = @_;
    my $notes = make_SoM_song($user_song);
    my @new_song = map {$SoM{$_} ? "$_ $SoM{$_}" : 'not a note'} @$notes;
    return \@new_song;
}

sub random_SoM_note {
    return $SoM{$notes[rand @notes]}{sound};
}

sub random_SoM_song {
    my ($number_of_notes) = @_;

    $number_of_notes ||= int(rand(100)) + 1;
    return [map {random_SoM_note()} 1 .. $number_of_notes];
}

sub note_to_sound {
    my ($note) = @_;
    
    return $SoM{$note}{sound};
}