how to force a script to return a 404 error?

[halayman]

I have two cases:
mydomain.com/script.cgi?string=validargument
mydomain.com/script.cgi?string=invalid

I need to add a code to my script to force a 404 error
like this

($nn,$argum)=split(/=/,$ENV{QUERY_STRING});
if ($argum="invalid")
{help code needed here to force a 404 error and exit the script.... no custom error messages please I need search engines to recognize the page doesn't exist at all};

thanks a lot

[adni18]

I'm not sure what you mean by 'force a 404 error'. Please rephrase.

[dmorison]

You could try something like:

print "Status: 404 Not Found\n\n"; 
exit 0; 

(providing that your script has not previously started any output of course)

[halayman]

thanks a lot dmorison
it works!