this happens sporadically with me and windows 2k. 
I write to model/wrl files and sometimes the browser  
doesn't render as it should. My fix is the following.
(Keep your perl script as is with the binmode STDOUT statement in place.)
In the html page type this:
<img src="mycounter.cgi?itlooksstupidbutsozwindows.jpg">
by ending my query string with anything.jpg or anything.wrl
i was able to convince my browser to stop spordically 
sending me non-text content as text.