new code .. will it work?

[Luinrandir Hernson]

Below is a piece of code that determines what web site you just came from.
I want to put a line in their that will exclude me

###here is the working code
if ($ENV{'HTTP_REFERER'} eq "" | '0')
       {$previous = "$ENV{'HTTP_HOST'}$ENV{'DOCUMENT_URI'}";}
       else
       {$previous = "$ENV{'HTTP_REFERER'}";}
###here is my new, untested code 
if ($previous eq "www.mywebsite.com/index/htm");
    {exit};

what I am hoping to do is to terminate the program when I enter my own web site.... 
ideas?is the above new code flawless???