$/ = ... # whatever
my @posts = <FH>;  # read all posts in at once and assign
		   # each to an array element.
my @keep_posts;
for(my $index = 0; $index < @posts; $index++)
{
	unless(defined($cgi->param("box$index"))
	{
		push @keep_posts, $posts[$index];
	}
}

	# open file... print all the kept ones out.
print NEW_FILE join("\n\n\n", @keep_posts);