use 5.010;
use strict;
use warnings;
use List::Util qw( max );

my %hash = (
  4 => 'The future is unknown.',
  1 => 'The day before yesterday sucked.',
  5 => 'Today is a good day.',
  3 => 'Not much hope for tomorrow.',
);

my $last = max keys %hash;

for my $line ( 1 .. $last ) {
    say exists $hash{$line} ? $hash{$line} : '';
}