> Isolate the problem, and wrap it in a test/unit. Then I can take a 
> closer look.
> 

The problem was a whitespace, which I did not see. I actually wrapped the output 
in apostrophs in order to see whitespaces. Since I am programming with cgi, I 
see the output in the browser window, which prints whitespaces very small.

Anyway thanks for the help!!

greets Boris