exit with out error ?

Hi,
Here is what am I trying to do:
I want my page to refresh it self every 5 seconds, but only if some file has changed in last 5 seconds. I can check that easy with Perl script, but problem begins when that file hasn't changed and in that case I don't want my page to refresh, so I would just exit the script with out printing anything to html.
And in that case this error appears: "Premature end of script headers"
How can I fix that?

Scrip is called by html in this way:

<meta http-equiv="Refresh" content="5; URL=http://www.upitnik.net/cgi-bin/test.pl">

If script does nothing when called, would above line call script every 5 seconds ?
If not, how could I do this what am I trying to do?

Tell your script to overwrite the line -> <meta http-equiv="Refresh" content="5; URL=http://www.upitnik.net/cgi-bin/test.pl"> so it doesn't refresh any longer.
The initial state when your script is called, tell it to print "<meta http-equiv="Refresh" content="5; URL=http://www.upitnik.net/cgi-bin/test.pl">"