HTTP headers and include()

I've written a separate function library for a cluster of web pages, and I then include("slib.php") in each of the web pages, instead of copying 12k of code to each page individually. Some of the pages require (simple) authentication or redirection headers, which some of the code in the library is supposed to handle. Problem is, when I include the library, even though there's no other output to be processed, it still generates the linefeed that triggers sending all the current headers, so if(!headers_sent) {...} fails. Is it possible to include php code without sending headers? I've tried exit() within the library, but that fails to work. Instead, exit causes generation of HTML code (a content type metatag) that is neither in the main page nor the library. I've also tried a simple return() (per the documentation), but that generates a parse error. I'm using Apache 1.3.12, PHP 4.0.2 and Slackware Linux (Not sure which kernel version). Thanks Cas PS: Please CC replies to casteele@innocent.com, since I'm not officially subscribed to this list. Thanks.