[plt-scheme] web-server servlet components not reloading

> > [cgi-bin]$ cat two.cgi
> > #! /bin/sh
> > string=? ; exec plt/bin/mzscheme -r $0
> > (printf "Content-Type: text/plain~a~n~a~n" #\return #\return)
> > (printf "test~n")
> 
> Did you try an absolute path for MzScheme?
> 

Yes, sir.  Still error 500.
Here are the permissions for mzscheme:

-rwxr-xr-x    1 kublai   site378     74519 Aug 11 10:31 mzscheme