use warnings;
use strict;
# variable we want to keep between runs
my $high_score=0;
my $play_it_again=1;

while ($play_it_again) {
    my $last_score = play_game;
    $high_score = $last_score if $last_score > $high_score; 
    $play_it_again=ask_user;
}

sub play_game {
    my $game_score=0;
    # game logic
    return $game_score;
}

sub ask_user {
    print "Do you want to play again (y or n)? ";
    my $play_again = <STDIN>;
    chomp($play_again);
    $play_again eq "y" ? 1 : 0
}