Teapot and Regex

Dear Smalltalkers (Pharonistas?),

while trying out teapot in Pharo4, I encountered the following: I have made a plain HTML form which sends data to a teapot URL. Here is what the browser is sending:

http://localhost:1701/bac/?a=88&r=0.7&kg=77

To answer this request via teapot, I wrote the following:

...
GET:'\/bac\/\?a=(\d*)&r=(\d*.\d*)&kg=(\d*)' asRegex -> [:req | BloodAlcoholCalculator a:(req at:1)  r:(req at:2)  kg:(req at:3) ];
...

But the answer in the Browser looks like:

Not Found /bac/?r=0.7&a=88&kg=77

I tested the regular expression via 'matchesRegex' and it returned 'true'. The funny thing is, that teapot changes the order of the values in the answer (r and a are switched). If I leave out the '\?' and use the resulting URL manually, teapot delivers the expected behaviour.

What could be the reason for this issue and where should I search to understand it (System Browser)?

Thanks for the attention and kind regards

Marcus