[basex-talk] Tumbling window

I have written the following code:

for tumbling window $s in ("this", "is", "an", "example", "." , "this", "is", "another", "[", "example", ".", "]", "Another", "example", ".") start $a when fn:true() end $b next $r when ($b = "." and $r = "]") or $b = "." return <s>{$s}</s>

which returns:

<s>this is an example .</s> <s>this is another [ example .</s> <s>] Another example .</s>

but I am looking for

<s>this is an example .</s> <s>this is another [ example . ]</s> <s>Another example .</s>

I am playing around with if-clauses, but I am wondering whether there is a more direct way to force the end of a sentence at "]" when it is preceded by "." or at "." when there is no following "]". Thanks.

Ciao, Giuseppe