sub Trueonce::TIESCALAR {
        my $s=1;
        bless \$s, $_[0];
}
sub Trueonce::FETCH {
        my($self)=@_;
        local $_=$$self;
        $$self=0;
        return $_;
}
sub Trueonce::STORE {}

##</code><code>##

tie $f, "Trueonce";
print $f, "\n";   # 1
print $f, "\n";   # 0 
print $f, "\n";   # 0
print $f, "\n";   # 0