Works fine for me, until I add the browser to the equation.

The program I used: 

#!/usr/bin/perl

$| = 1;

print <<'END_HTML';
Content-type: text/html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<head>
<title>PAGE TITLE</title>
</head>
<body>
<p>Start.
END_HTML

sleep(5);

print <<'END_HTML';
<p>done.

</BODY>
</HTML>
END_HTML

[download]

Running it from the prompt: 

$ foo.cgi
Content-type: text/html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<head>
<title>PAGE TITLE</title>
</head>
<body>
<p>Start.
...waits 5 secs...
<p>done.

</BODY>
</HTML>

[download]

Running it from via the web server: 

$ telnet www.example.com 80
Trying 11.22.33.44...
Connected to www.example.com.
Escape character is '^]'.
GET /script.cgi HTTP/1.0
Host: www.example.com

HTTP/1.1 200 OK
Date: Mon, 17 Dec 2007 22:39:09 GMT
Server: Apache/2.0.54 (Unix) PHP/4.4.7 mod_ssl/2.0.54 OpenSSL/0.9.7e m
+od_fastcgi/2.4.2 DAV/2 SVN/1.4.2
Vary: Accept-Encoding
Connection: close
Content-Type: text/html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<head>
<title>PAGE TITLE</title>
</head>
<body>
<p>Start.
...waits 5 secs...
<p>done.

</BODY>
</HTML>
Connection closed by foreign host.

[download]

But when viewed in FireFox 2, it waits for the entire document to arrive before display it.

In reply to Re: I think I'm misunderstanding $| by ikegami
in thread I think I'm misunderstanding $| by sigmazero13

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