use strict;

my $list        = undef;
my $lastnode    = \$list;

while (1)
{
    print '<i>nput, <o>utput : ';
    chomp (my $input = <STDIN>);
    
    if ($input eq  'i')
    {
        &add;
        next;
    }        

    if ($input eq 'o')
    {
        &show;
        next;
    }
}

sub add
{
    chomp (my $input = <STDIN>);

    my $newnode = [undef, $input];
    $$lastnode  = $newnode;
    $lastnode   = \$newnode -> [0];  
}    

sub show
{
    for (my $node = $list; $node; $node = $node -> [0])
    {
        print $node -> [1] . "\n";
    }
}