my $frame = 10;
my @buffer;
$, = ' ';
$\ = "\n";
while (<>) {
    my @row = split;
    if (@buffer and ($buffer[-1][0] < $row[0]) ^ ($buffer[-1][1] < $row[1]) ) {
        pop @buffer;
    } else {
        print @{shift @buffer} if $frame < push @buffer, \@row;
    }
}
print @$_ for @buffer