UIMA Ruta use of features in a block statement

[Lisa Langnickel]

Hi, 

I would like to use a BLOCK statement to iterate over the values of a feature.
In more detail, I applied a lemmatizer before and would like to work on the 
"lemmas" itself.

I tried something like this (where Lemma.wordLemma describes the feature of 
Lemma):

BLOCK(forEACH) Lemma.wordLemma{}{
    Document{-> MATCHEDTEXT(s), ASSIGN(a,contains(s,"vergess"))};
    Document{a -> Value2};
}

There is no error message, but nothing happens. Instead, when only working on 
the type "Lemma", it works. 

Is there any possibility to work on the feature within the block statement? 

Thanks in advance, 
Lisa