use strict;
my @buffer=(
        {
        data=>'',
        next=>1
        },{
        data=>'',
        next=>2,
        },{
        data=>'',
        next=>3
        },
        {
        data=>'',
        next=>4
        }
        );
sub store {
        if($buffer[$tail]{next} !=$head){
                $buffer[$tail]{data}=shift;
                $tail=$buffer[$tail]{next};
                
                return 1
                }else{
                        return "Buffer is full";
                        }
        }

sub retrieve{
        if($tail != $head){
                my $data=$buffer[$head]{data};
                $head=$buffer[$head]{next};
                return $data;
                }else{
                        return "Empty\n";
                        }
        }
        
store "20";
print retrieve;