First, you should be able to turn autoflush on for the filehandle you're using to output (see my example above). That should ensure that whatever you write to the file gets flushed immediately.

Second, yes, you should be able to flush the clipboard with the line: $clipboard->Empty();

Type "perldoc Win32::Clipboard" at your Windows Command prompt to read more about the Clipboard module. I would recommend taking a look at POSIX::strftime for formatting your date/time into a file name. Here's an updated version of the script that uses strftime. It creates an output file with a name like: clip_2001_Aug_21_15_51_11.txt but of course you can customize any way you like.

#!/bin/perl -w
use strict;
use Win32::Clipboard;
use FileHandle;
use POSIX;

my $clipboard = Win32::Clipboard();

print "To exit, CNTL-C out of this window.\n\n\n";

$clipboard->Empty();
while (1) {
    $clipboard->WaitForChange();
    my $text = $clipboard->GetText();
    
    my $now = localtime();
    my $file = POSIX::strftime("c:\\temp\\clip_%Y_%b_%d_%H_%M_%S.txt",
+localtime());
    open(OUTPUT,">$file") or die "open: $!";
    binmode OUTPUT;
    autoflush OUTPUT 1;

    print "$now: writing " , substr($text,0,40) , "... to $file\n";
    print OUTPUT "$now\n$text\n";
    close OUTPUT || die "close: $!";
}

exit;
[download]

Note, I noticed that on my system (Win2K, ActiveState build 623) that this write a file as soon as it's run even though the clipboard hasn't changed. I'm not sure why that is -- it seems to work fine once it's running. This should get you started though.